People complain here on HN that public or semi-public telegram groups are not e2e encrypted. Yes, your HN comment isn't either. And there is no point in encrypting it if its mean to be read by others. Telegram isn't just a messenger. Its a social media like platform with millions of groups and channels you can find trough telegram or they are linked form other places.

Would there be a use case for a fully private e2e group chat? sure, I have a family chat which probably counts as fully private. But even if it could be e2e it would not be because my family wants to have backups and seamless switch between devices. They are also unable to reliable protect they devices form third party accesses trough malware/spyware etc. All my other groups are public or semi public (means link can only be found if you are part of the right internet community) The messages there are no other than the comments here.