I tried to comment to this user, trying to ask why he left non-commented links in comments, that were links to the question itself.
I got the message
Comments cannot contain that content:
After rewording and rewording I noticed this is because of the content of the user's name that gets inserted by typing @+C+Tab.
How can I comment to this user without using the (blocked) full name in a way that he will be notified of being addressed?
For now I flagged the link-only comments, that are without any explanation, as non-constructive. But I rather ask the poster for an explanation of intentions and potentially improve his commenting behaviour.