Is it possible to
@ multiple people simultaneously? I tried to use
@ for the second time, but auto completion doesn't show up for the second
@, so not sure about it.
It's not, and you'll get an error if you try to submit a comment with multiple targets:
The error is reminding you that there's no need to @target the post owner; they get a notification no matter what. So if you @target a commenter, both the commenter and the post owner will get a notification, but you can't ping two commenters