This chat usually notifies about Telegram updates. If I mark it as read, delete (either "for me" or "for me and Telegram") and after a while refresh the page, it reappears within a few seconds with (1) unread bagde as in a screenshot, at the top of my chat list. No new messages are there, so this is probably a bug. Also exists in K version. Noticed it about a week or two ago.
Telegram Web 1.51.1 Z, Opera 90