When someone is on vacation, it is not possible for others to know about it when they tag someone in notifications. That would be useful to inform colleagues that a person is on vacation and tagged as such when writing to them in the notifications. Lately, a colleague wrote to me and there was no way she can see that I was on vacation. It is someone else that had to inform this colleague that I was out of the office. It can be editable so the person can write personal information: out of office - on vacation - back on XXX, or else. Emails have that, and other apps do have that feature too. For example, Slack is one of them.
Thanks for considering.