Over the past several weeks, moderator comment deletion has been regular and heavy handed. I'm generally good with this (I'm on record as saying I'm far more likely to delete an entire comment stream than a few single comments when it's my job). But it would be good to both evaluate this behavior to make sure it continues to be constructive, and to enact some reasonable limitations on the policy.
Some data on recent comment deletions would be really good. I don't think this is available in the data explorer, but perhaps the community team could be called upon to provide it?
There are a few types of comments that rarely merit deletion and can be harmful if they are deleted. It would be good to make sure that these kinds of comments are not getting deleted:
Comments that indicate an answer is incorrect.
Comments that point to an uncorrected flaw.
Comments that add additional sources that have not yet been edited into an answer.
Generally if these comments lead to a stream of discussion this is not constructive, but when it's a single comment or two pointing to flaws/incorrect assumptions/flat wrong details, they are important supplements to upvotes and alternate answers and should be preserved.
When we are trying to provide good information to people, comments that are critical of an answer, that correct flaws and provide sources are important tools for both readers and voters to properly evaluate whether the answer is correct or not. Generally moderators are not supposed to be making these judgements so comments that are critical of answers should stand.
Ultimately without the data to know how many of these kinds of things are being deleted it's hard to make a judgement. However, the sentiments of several people in chat are that critical and otherwise useful comments on answers are being deleted and that this is harmful to the site. It would be helpful if we had access to the data to evaluate our comment deletion practices.
As far as data, a random sample of comment (or comment stream) deletions from the past 30 days would probably be sufficient to try to determine how the current comment deletion campaign is going and if there are any adjustments that need to be made.
To be clear. I am NOT arguing the preservation of extended discussions. I am requesting data on comment deletions and ultimately a preservation of singular comments or short exchanges that add useful information or correct errors.
Comment deletion is about to become a whole lot less important in general. There is a pending feature request that will prevent old comments from showing up, much the way that they do on questions with more than 30 answers (I'm working on getting a timeline for this, I'll report back when I've got a better idea of when it will be implemented). This means moderators can spend a lot less time dealing with comments and the site will still look very clean.