I know you want comments to be transient, temporary repositories of brief requests for clarification that should disappear when the parent post is edited to address the commenter's concerns... but, sorry, that simply isn't what happens in reality.
In reality, comments contain threads of text that may be valuable for any of the following reasons:
- they add information to the post in a tangential fashion
- they display hilarity and/or wit, brightening my day
- they have lots of upvotes and this has happened because they deserved them
- they were written by people who spent time doing so to add value to the parent post, possibly in the form of a little note or a pleasant remark
Comment threads that devolve into shameless name-calling should quite rightly be moderated away into oblivion, but I am not so sure about the marginally off-topic or ever-so-slightly-narky remarks that are more than slightly amusing, serving to lighten ones mood, but are then removed anyway … and take the comment thread's context with them!
Now, moderators can still see deleted comments, suggesting that these comments still exist in some reasonably convenient form in Stack Exchange's computer memory databanks.
Could 30k+ users be allowed to see deleted comments, please?
Let 874 of your finest programmer and developer friends indulge in a little illicit comment fun.
Go on, you know you want to...