How can one send comment to two participants X and Y simultaneously?
Does the following works
@X (and @Y).
I learned this from some messages by moderatores in meta. but I am not sure it works for all participants.
In general, you can't. However, the author of the post will automatically receive inbox notification without the @name syntax. If user A is the author, and you want to reach user B as well (someone who has participated in the thread, via edit or comment), then by typing @B, both A and B will be notified. But if B has not participated in the post discussion, then B cannot be reached this way.