I know that sometimes if you want a specific user to be notified by a comment, you have to put @so and so. But can someone explain to me when that is and isn't necessary? Thanks!
Canonical meta.SO thread How do comment @replies work? has everything you wanted to know about comment notifications and much more. Basically, you don't need to include @ in two cases:
- you are addressing the owner of the post under which you comment.
- you are commenting on your own post, on which only one other user commented so far.
In case 1, if you are not the first one to comment, you may still decide to use @ for the sake of clarity. The system will let you do so in this situation; but otherwise @ is automatically removed when it's unnecessary.