There is no way to catch events when attachment was added/removed.

If attachment was added in the comments, it doesn't count as issue update nor Attachments field change, so the respective triggers don't work.

We need a trigger that specifically looks at the count of the attachments under Attachments. If there was one attachment added (via comment or directly to the field), then the count of attachments increases, so it would work as a trigger.

This would be very helpful for the cases, when people have to provide attachments when dealing with requests.