I do not know if this is the right place to ask the following question, but couldn't find the answer anywhere else either. So please delete the question if it is out of scope for this community.
I have a question which I asked on MMSE some time back. Today I went to one of the answers and tried to add a comment to which I wanted to tag the person who answered. However I was unable to do so as adding the
@ symbol and typing the name didn't show the user name of the person. Is there a specific time limit within which tagging can be done? Or is this something else?