The tag is present in Lintian version 2.109.22. That is the most recent version we know about.
Debconf notes should be used only for important notes that the user really should see, since debconf will go to great pains to make sure the user sees it.
Displaying a note with a low priority is conflicting with this statement, since using a low or medium priority shows that the note is not important.
The right fix is NOT to increase the priority of the note, but to move it somewhere else in the inline documentation, for example in a README.Debian file for notes about package usability or NEWS.Debian for changes in the package behavior, or to simply drop it if it is not needed (e.g. "welcome" notes). Changing the templates type to "error" can also be appropriate, such as for input validation errors.
Please refer to Debian Policy Manual section 3.9.1 for details.