It will be a solid proof if you show us a screenshot of the telegram ID and quote a post where he had posted the same telegram ID in here in forum.
You can follow the link to his group and check everything there.
He posts his advert in his group, he doesn't post here.
Edit: I can't quote a post where he mentioned his telegram name because the thread has been locked but here is the link to the thread
https://bitcointalk.org/index.php?topic=5182812.0
Screenshot of his ID
