I’m not having much luck getting it to fire on @mentions, though it does seem okay with plain usernames. I think that might lead to some unnecessary ones though. But even with @mentions it could just start replying when you didn’t intend it to (eg. ‘@BryanV gave some good advice in this topic…’ → ‘Hello, I’m on sabbatical…’)
I was wondering if another feature might make it clearer you’re not available? I think the holiday calendar feature of the Calendar (and Event) Plugin could be useful to apply some notes and emojis to your username wherever they appear, including in the composer when someone starts to write an @mention to you. This would let people know before rather than after posting (and avoid some auto-reply noise).
There’s also the User Status (enable user status) if installing a plugin was out of the running. You can also be more specific about your reason for not being available:
You can’t restrict its use to only certain groups, but you can hide the UI from non-staff with something like this in a theme component:
.set-user-status {
display: none;
}
.staff{
.set-user-status {
display: initial;
}
}