Dear Fastmal, I am a happy customer, but very concerned by this report. Would you mind to comment?
No, but if you visit your Threads page (link at the top of every page) you can see any replies to any of your comments. There's nothing special that marks a new reply, though.
I have a habit of upvoting nearly every reply anyone makes to any comment of mine, as a way of thanking them for the comment. This also happens to help when I skim my Threads page, since it's easy to spot comments that still have the voting button(s).
Being able to persuade a customer service rep to provide access to an account (even if indirectly by changing a recovery email) should never be possible.