en.wiki does not have the issue.
- On any Talk page in ca.wiki or test.wiki - e.g. http://test.wikimedia.beta.wmflabs.org/wiki/Talk:Mavetuna or http://ca.wikipedia.beta.wmflabs.org/wiki/Discussi%C3%B3:DT6 - click on the Mention icon, select a suggestion and click Insert.
- There is no visible insert of Mention in UI. Switch to wikitext - the inserted template is displayed.
Clicking 'Save changes' in VE mode, saves the added Mention.