I keep forgetting we have this function. Just remembered to use it in a post to attract those members I mentioned . If you put a @ then the members user name then they will be tagged in that post . Helps other members link to their profile . For example if I want to alert Clive to a post about matches & petrol & can put @CL1 I think the tagged member gets a notification, can someone tag me just so I can check.
Looks like the person tagged needs to already be following the thread... which is quite bizarre. Might be a setting, but suspect it may be to protect people from tagging abuse on the madder sort of forum.
From what I've found elsewhere: If someone is watching a thread, they won't receive a mention alert as the new reply alert 'overrides' this. If someone is quoted and tagged, they'll get an alert for the quote and not the tag. If a post is edited and a tag is added afterwards, no alert will be sent. If someone tags say 10 people and the user group tagging permission is set to say 5, then only 5 people will get the tag alerts. Further, users can opt out of alerts via: Profile > Alerts > Alert Preferences > Receive an alert when... someone mentions you in a message [tick/untick box]