In my preferences, favourites is for tracking questions I have a personal interest in, and I don't like putting questions that need work in that list, partly because I want it to be full of interesting and useful stuff, and partly because I don't like to give a star to a question that needs work.
track this like it's mine
Maybe this could be achieved with a "track this" button, whereby a Q or A you track puts something into your inbox, much as you would get notified if your own question/answer was edited or commented upon.
Advantages: may be straightforward to implement, by editing the code that notifies the poster of changes to look up a list of interested users.
Disadvantages: some people may fill their inbox with noise and start ignoring it or getting grumpy. You'd probably still need a list anyway so you could review and unfollow.
watch like favourites, but less fondly
Maybe this could be achieved with a "Watched" list similar to but separate from the favourites list, consisting of questions where you have a comment with a questionmark.
If your question is answered, you can delete the comment to stop following the question, thus clearing up the comments in the process.
The list would show a change when a new comment is added or the question is edited (some OPs answer comments in comments rather than edit the question).
There would be no star or visible sign the question/answer was being watched.
Advantages: Re-use of existing favourites code
Disadvantages: People will be confused about why there are two ways to do essentially the same thing
[Feel free to comment with further advantages and disadvantages, or indeed with which you think is best.]