"Mentions" hyperlinks are set up when the words "work item" and then the ID number are used in the Summary, Description or Discussion fields. Also, I've seen "mentions links" created when you have the work item type followed by a number in these fields.
To make sure you don't get these mentions links created, you'll have to look at the Summary, Description, and Discussion fields and be sure that if a work item type is followed by a number, you put in a character that defeats that pattern (like an underscore instead of a space between the work item type and the number).
Hope this helps.
