Idea
automatically watch cards you add or edit+status
automatically watch cards you add or edit+priority
automatically watch cards you add or edit+tag
automatically watch cards you add or edit+issues
Lots of use cases. A current one is that people file support tickets and then don't know when we've replied.
automatically watch cards you add or edit+solution
When you add or edit a card, to the right of cancel is a checkbox with "Receive email when this card is edited by others." If it is checked when they save, add/update +*watchers as appropriate.
No checkbox when editing/adding cardtype cards.
automatically watch cards you add or edit+discussed in support tickets
automatically watch cards you add or edit+relevant user stories