Even if there are alternative ways to see the content of the comments, making it more difficult to access that content still does something and isn’t pointless. The average person isn’t going to go through the trouble of checking the wayback machine or some other external archive, or download any add-ons or what have you to undelete or unedit comments. Not unless they already know that the comment said something they’re interested in enough to put in that extra effort, which is going to be a pretty small selection of people who might but probably won’t look into your comments unprompted to begin with anyway.