Yeah, I can see how that would be a pretty big negative. Didn't occur to me at all.
If they were as easy to edit as posts, I'd have no problem with them. But we had to go into a user's profile (the recipient's, not the giver's) to edit, which is handled through a completely different interface than the one we use for posts - so a separate login and several more clicks to get through the process.
Which is not to say that we shouldn't show comments. I merely speak to my own experience with them, 'cause we are chatting and all. Maybe other solutions will come to mind.
For example, if there's a way to turn off showing XP comments we receive, maybe mods and admins should turn them off as a general policy. Or maybe folks feel that while commenting on moderation in-thread is generally a bad thing, maybe a simple "Thanks" to a mod when they do step in and folks like how it was handled is acceptable? I'm not a fan of that last last - but I'm probably the biggest stickler on the staff.