On reddit, one can simply type u/me or r/reddit - I can see mentions of /u/user or /c/community in descriptions but doesn’t seem to mention a sublemmy like a subreddit.
Also, can’t seem to share a Lemmy Profile with their URL like for mine as example.
for users use @ and start typing the name, for communities use ! and start typing the name.
Also wrong community for lemmy support questions.