Is it in the User menu, or presented as a Tab?
If it is in the menu, then it sounds to me like it ended up there from the JomComment component, and not this one.
So that when you Uninstall the JomComment there is often still this menu option left there without the component as landing page.
If this is the case, just go to Menus > User menu and Unpublish or delete (Remove) that menu called My Comments (:: Mycomments).
If it is a Tab option, the procedure is almost the same, just look in your Tab options of your CB Backend.