Do comments have revisions like posts and pages? If so, how would you access those revisions?

No, WordPress only provides revisions for posts.

The “History” link on the admin/comments page does not show any editing/changing/updating of the comment, whether done by the admin or the original commenter.

This is actually added by Akismet and not something WordPress itself provides. It acts as a moderation history of sorts, but only Akismet related actions e.g.

Note that I’d edited the comment pictured, yet that edit was not recorded.