Ok, I am going to throw some ideas out in this answer, because it is too long for a comment.
I am going to use owod and cwod interchangably throughout this post.
They are the same thing,
owod == old world of darkness (opposite of nwod),
cwod == classic world of darkness
owod 1st ed, owod revised, owod 20th anniversary.
As I understand it, revised just incorporates more or less an errata.
20th anniversary incorporates another errata, and adds rules for things that weren't invented when owod first came out -- like mobile phones and the internet.
Thus these all deserve one-tag between them,
if it matters that a question is not using the errata then it can be clarified in the post.
(Correct me if I am wrong, I am not really too cluey about oWoD, I'll mark this community wiki).
Commonality between all three systems(owod, nwod 1.0, nwod 2.0):
They all have vampires, wizards, werewolves...
but so does Dresden-files. So does Buffy. So does Supernatural. (all of which have RPGs).
Things that are common between all 3 editions, are common in all urban fantasy. If someone is in a situation where they have a question that general,
they should use a more generic tag.
("What does the average modern person know about vampires?" would go under a urban-fantasy tag (since it is actually asking about characters, who are in the dark about setting specific elements anyway) , "How to create dark atmosphere?" would go under a gm-techniques and maybe horror)
But really, they are not asking a WoD question at this point.
There is no real usecase for a tag for setting elements common across all 3 editions.
Setting elements the asker assumes (or even knows) to be common to both editions should use the tag for the game they are playing. Since they could be wrong about that assumption, and it could change with new books coming out.
If the goal is to compare elements between the editions, eg "What happend to the Malkavian Clan?" then this is a good use for using two tags. It is specifically to two editions.
When WoD reachs truely deep numbers of editions like dnd has, by that stage it might be worth having a global world-of-darkness that is for questions like "How have vampires changed across WoD editions?", but for now that isn't useful.
It is better to not have that global tag their to confuse people.
The rules are boardly similar,
but so are the rules for Sion and Exhalted.
In general small difference in rules matter.
People come to the site when things are unclear,
and alot of that time it is boarder cases when things are unclear.
Small differences in rules matter enough for the tagging to change.
The exception being if the difference is from using an erata, as I suggest the owod editions are, and that nwod-gmc is not.
(Dark Heresy for example has had 3 erratas, we do not have 4 different DH tags)
So common rules is no motivation for a common tag.
No reason for a common tag across all 3 editions.
- Common Setting elements are also common to all urban-fantasy
- Rules are not similar enough to be useful
The only concrete thing they have in common is the current rights holder
(not even a common publisher).
and any question that is onyx-path-publishing, is going to be along the lines of "What is Onyx Path's policy on Fan-created Books?", not a WoD question at all.
nwod 1.0 vs nwod 2.0
See discussion: Lets get a clear consensus on the use of [nwod] vs [nwod-god-machine]
The issue we have right now, is that over the next few years, onyx path will finish republishing all the content they intend to cross over.
Right now there is the implict (and sometimes explict) understanding that most nwod 1.0 supernaturals are assumed to exist in nwod 2.0.
Eventually, all of them will come across.
But as we have seen with Vampire, and from what I have heard of Werewolf,
and from how Second Sight minors were merged into core, they will not make the transition without major changes.
Such questions have the final purpose of being used with nwod-2.0 and should be tagged as such.
Given time, the new books will be out and they will have canonical nwod-2.0 answers, that will be better than anything from nwod-1.0.
People looking to answer will for now be familiar with both systems, and by the time that is no longer the case, all content that is going to be offically republished will have been.
Thus in those cases nwod-2.0 is all that is needed.
This is distinct from questions specifically about the differenced between nwod-1.0 and nwod-2.0 which definately should be tagged with both.
There is also the case of asking how to do the conversion, which is more problematic, think should be tagged with both, (I don't know if we have seen any such questions though so this may be moot)
Questions that are for final use with nwod-2.0 include:
- Qashmallim, and the similarity to Angels? : which will actually I believe be concretely answered in the Promethean: The Created Second Edition, coming out in Spring. Til then speculation can be made based on the existing nwod-1.0 books. But it is speculation.
- How can I make a shapeshifter that takes human forms? The question asker is playing nwod-2.0, but is willing to port content from 1.0. Since as GM he can create new supernaturals, and since is is going to have to do alot of rules work anyway, limiting the scope to things that have appeared in a past edition of the setting is likely unnesc. He just wants to know about shape-shifting monsters. This question I think might be better tagged: [nwod-god-machine] [urban-fantasy]
We will be wrong
An issue we will see with questions about 1.0 setting elements in 2.0, is that we will be wrong. That is Ok however, so long as it is clear.
If someone had asked me before Blood and Smoke (aka VTR 2.0) came out: "Could I have a GMC plot, where the party ambusses vampires while they are sleeping and kills them by openind the blinds?, I am willing to port content from 1.0", I would say "Sure here are the 1.0 rules that support this idea. It will be a fairly easy fight, so easy that I don't think vampires would be foolish enough to be in such a position" but now with 2.0 my answer would be: "Sure, but it will be hard. Sunlight hurts vampires abit, but not enough to disable them before they kill half the party. Their occult checked should tell them this. They might be better off barricading the doors and torching the place."
Some questions will be unanswerable:
"If a changeling takes a physical condition, eg Blinded, with-in a dreamfight, what happens when he wakes up?"
We can speculate but can not answer.
We strongly expect there to be changeling in God Machine, but we have no rules.
I think between nwod-1.0 and nwod-2.0 we are doing the right thing.
I asked about this in Lets get a clear consensus on the use of [nwod] vs [nwod-god-machine]
I believe there is enough clearness there to solve any issues.
Applying it to the example questions:
- Qashmallim, and the similarity to Angels? This is actually a different question dependign on if it is tagged nwod-1.0 or nwod-2.0. It if it about nwod-1.0 then the answer will be based on the Sample Adventure from Saturnine Night and on the core "Secret Histories", if it is nwod-2.0 then it is based on the paragraph from GMC-RU and whatever can be gleaned from demon, as well as the upcoming Promethean 2nd edition. If it is tagged both then it can not get a really good answer. Because the God Machine is presented differently between the books.
- How can I make a shapeshifter that takes human forms? This question is very broad. It is asking about something to use with nwod-2.0. It wants to take inspiration from nwod-1.0, but it is for nwod-2.0. The nwod-1.0 tag might attract people from 1.0 who can answer, but that is similar to asking a question about zsh and also tagging it bash on Unix.SE. While answers for bash might help and you might be willing to convert them, its not actually about bash
- Does Blood and Smoke invalidate previous Vampire books? is the a listed example of something that should use both, it is asking wether books from one can be used for the other (and the answer is no)