BuddyPress.org

What do you mean by brackets?
1 ( these )
2 { these }
3 [ these ]
or something else?

What’s happening when users try to use them? And in what context are they using them, activity updates or forum posts or profile fields or what?

And what version of BP/WP are you running? https://buddypress.org/community/groups/how-to-and-troubleshooting/forum/topic/when-asking-for-support/