I've figured out via this forum how to mention users, and its working. The only thing is that there's no email send when users are mentioned? Should I activate this somewhere? At 'tools - emails' it is activated to be send. I did get an email yesterday, but as far as I know I didn't tag myself at that moment. Now I've deliberately tagged people and nobody gets an email.
Im talking about this forum (but it's shielded off for anybody who isn't logged in) https://www.stadscooperatieassen.nl/community/
Please navigate to Dashboard > Forums > Settings > Emails admin page, on the bottom of the page you'll find User Mentioning Email section, just make sure "Enable Email Notification" option is enabled there.
Did some further testing to try find a nexus.
In tests an email notice is triggered if the mention has text on the same line as the mention name. If the mention is on its own line (like on this reply to you) and the reply text is in the next paragraph no email notice is triggered. (You should be able to confirm that you received no mention notice from this reply.)
If the mention name is on its own line but is suffixed with a period (.) or a comma (,) and the reply is in the next paragraph then an email notice is triggered.
If the mention name line is copied and pasted eg: (@mention-name) an email notice is triggered.
A case can be made that the mention name should auto insert either a comma or period upon reply.
That is a subscription notice, not a mention notice in your attachment.
I did receive the mention notice on your new reply but from my testing that reply format does not work on quite a few of the WPforo boards I admin. I am not sure where to debug the problem.