If moderators can view and undelete comments, can we see comments we've deleted? We can see our deleted answers, but why not our deleted comments?
Moderators need to be able to see deleted comments so that they can respond to complaints and reconstruct arguments / detect trolling/harassment/rage-quitting. Sadly, all of this is common enough that it required additional tooling to support.
Moderators don't actually need to be able to undelete comments... However, it makes comment moderation much, much faster - particularly when a handful of constructive comments are buried deep within a long, tangential or argumentative thread. Yup, that's right: it's often faster to delete everything and restore a handful of useful comments than it is to delete only the cruft.
For most intents and purposes, deleted comments are gone - you should try your best to put anything of value into an actual answer. As you note, you can view your own deleted answers, as well as their revision histories and such - if you need or want that functionality, use answers rather than comments.
Yes, I agree - This needs to be reviewed again. Users should be able to view all their deleted comments in their profile (just as we can view our own deleted questions and answers).
A good place to show this can be in Profile > Activity > All Actions > Comments (comments that have been deleted can be shown as 'deleted by so-and-so-mod').
The argument I make for this is that:
- it can increase fairness and transparency in moderation.
- it can inspire the user to expand the comment into an answer.
I am a frequent participant at Politics.SE, and due to the nature of the subject, there are often questions that are highly active and see a lot of user interactions. The answers also often tend to turn into discussions in comments. Often, many of these comments are rightly deleted, if they aren't pertinent to improving the answer. Though sometimes, I have suspected political bias to be a stronger reason behind the deletion of some comments. However, due to the inability to view a history of deleted comments, users can't really present a strong case (in Meta) that a mod abuse may be happening. (This may not necessarily be intentional - sometimes the political bias can be unconscious too, and a historical view of deleted comments of a user can reveal a pattern of this).
The second argument in favour of allowing the user to view deleted comments is that the info in it can sometimes help them expand the comments into an answer. As I pointed, despite SEs being a Q&A platform, Politics.SE sees a lot of discussions in comments. And sometimes, I have found that when I too post a comment critiquing or praising a question or answer, I sometimes post some good info that inspires me to write my own answer later. But if the comment is deleted by the time you decide that, it can be a bit frustrating to not be able to refer to it again.
In addition - sometimes you get feedbacks to your own questions and answer, and reply to some comment in your own question or answer. And you may wish to add that to the Q or A. Lack of access to deleted comments means you have to recall and rewrite everything again instead of simple copy - pasting and refining it. (Not everyone is good at expressing themselves well in written communication, and sometimes it is an effort.)