I have the 10k privilege of seeing deleted posts on Math.SE. If I have bookmarked a question, and it is later deleted, I can still see it in my bookmark list (although it is visibly marked as deleted), see below image for an example:
However, when I have made comments on a question, and that question has since been deleted, that comment is no longer visible in my comment history on my own profile. It bothers me when I made a comment an hour ago and can no longer go back to it. It bothers me because I am a little sentimental and some times go back in my comment history just and relive the fond memories. It bothers me because other 10k+ users can happen across a comment that I have made, that is signed by my name, and I have no centralized place to monitor that part of my public image.
Regardless of why it bothers me personally, those of my comments that were posted below questions (and presumably answers) that have since been deleted don't appear in my comment history. Even if they are viewable by me should I happen across that page in a different manner.
If I can see those comments on that post, and other 10k+ users can see those comments, it seems very reasonable to me that they should appear in my comment history. Presumably marked in a similar manner to the above screenshot.
One could consider extending this so that 10k+ users can also view such comments on other people's comment histories. This still won't give them access to anything they didn't already have access to, it just gathers it in a place where it is reasonable to expect to find it. I'm also entirely fine if this is an opt-in that is hidden behind a checkbox option or a separate tab or something, as long as it is discoverable.