When creating a new record and trying to use the @mention functionality on a journal input type field such as comments or work notes it does not work. Nothing simply happens instead of the @mention popping up to allow the user to search which users to mention.
This is expected behavior since @mention does not work for new records as journal input type fields on a new record form do not use UI16 activity stream. @mention will work correctly on existing records as long as the journal input type fields use UI16 activity stream.
Create the record first and then @mention will work correctly as expected.
Make sure to confirm that the journal input type fields are added to the UI16 activity stream.
@mention can also be disabled for specific tables by using the "live_feed=false" attribute on the table's collection type dictionary.