DISCLAIMER: as you may guess by looking at my profile history, I can't really be considered an experienced user of this specific site in the network. Nevertheless, I have been an user on the network for quite a long time now and have seen this topic come up many other times on various of its topic-specific sites, so please accept my answer as something more generic and not centered around just Role-playing Games.
So, you have found some content on the network. You read it, and reading it makes you feel bad. For some reason, the tone in the post doesn't feel right: maybe there is a bad joke that some could find offensive, maybe an answer look far too condescending on the asker, maybe it is something different but the final outcome does not change... that content simply doesn't feel nice...
...but the post also provides some useful info, so you fear that removing it would mean losing good content too. At this point, you don't know what to do... the best option seem to be editing out the "bad" part of the post, re-writing it to remove whatever felt out of place, but you also fear this could be impolite to the original poster - after all you are changing their "words" and original intentions to something you think is more fitting.
I fear I can't really give you a gold-bullet clear cut answer on what to do in those cases, but I hope to be at least able to give you some suggestions on how to start.
First of all... Don't be afraid - your intentions are good.
You aren't thinking about changing the content of a post to misrepresent the original intentions of its author - you are just trying to improve an existing post so that no one will feel bad or put-down by reading it. There is no evil in this.
If you really still feel dubious about this, consider that the network Code of Conduct states this:
No subtle put-downs or unfriendly language.
Even if you don’t intend it, this can have a negative impact on others.
No name-calling or personal attacks.
Focus on the content, not the person. This includes terms that feel personal even when they're applied to content (e.g. “lazy”).
We don’t tolerate any language likely to offend or alienate people based on race, gender, sexual orientation, or religion — and those are just a few examples. When in doubt, just don’t.
This includes, but isn’t limited to: bullying, intimidation, vulgar language, direct or indirect threats, sexually suggestive remarks, patterns of inappropriate social contact, and sustained disruptions of discussion.
I had to cut some of the actual text for sake of brevity (refer to the above link for the full version) but I think the general meaning should be clear. We should strive for this to be a welcoming place for everyone and there is no "site culture" that can override this (luckily, "site culture" - as in "our site tolerates this - we are grown up!" - doesn't seem to be a problem I have really seen on RPG - as I said before you guys still feel like one of the best communities I have found on this network).
That said... it may be hard to judge at times. Maybe you think you may be a little oversensitive (I know this felling very well, back on Meta I was considered very oversensitive on some topics by far), maybe you wonder if you have misinterpreted the post, maybe there is something else you don't know... "maybe".
Well... let me tell you a thing.
You are not alone in this.
When in doubt... just ask. You have many ways to do so.
- you can raise a custom moderator flag: tell the mods you feel this post could be improved and let them handle the problem from there. This can be good at times - first, they probably are more experienced than the average user when it comes to moderating stuff (hey, they are moderators, after all). Second, if moderation will be really needed often corrective actions performed by mods are more easily accepted by the user than the same action being performed by some "generic internet person".
- for simpler task, it may just be worth double checking your thoughts with somebody else. In this regard, chat is a good place to ask for advice. "When in doubt, ask our local guru BESW" they say.... Jokes aside, never underestimate the power of asking for advice (unless you are a candy colored ponies and have to fill a 21' episode with a friendship problem that would never have existed if you just talked from the start).
Either way as I have said before, just ask and I am sure you will find someone willing to help you to dispel your doubts and hopefully work together for choosing the best course of actions.
As a last suggestion, when asking please always keep in mind what should be your first objective: you aren't trying to "demonize" anyone - so try to avoid what could be seen as name-calling, superfluous "bad advertising" of an user or just seeds for drama and flames. What I mean is that you should focus on the fact that there is some not-nice content on the site - not on the fact that "user X" posted some not-nice content on the site. It is true that sometimes moderators will have to focus on a specific user when deciding corrective actions (as you may understand, it does matter in a way if said user is just having a bad day or is a user which already had a history of multiple suspensions for offending other users), but focusing on "who" did post the bad content isn't probably something that you should do when asking for advice (or when you aren't even sure that it's bad content in the first place).