I have to congratulate the team for making the synths tab of the profile page the default again, (hopefully we won't have any more people wondering how to find their synths). I do understand what you were trying to do before, though, by bubbling up recent comments on our synths to us. As a compromise, would you consider listing the number of comments that have been made since the last time that we were logged into our account and loaded those tabs|pages|synths next to 'Activity on Synths' and 'Replies to Comments'?
It's a common feature on forum software to display the number of unread posts in topics that I've bookmarked. Similarly, when we log into our email we see the number of unread emails in our various folders. With that sort of interaction already familiar to people, I've been thinking that it makes sense on our profile tabs as well.
Food for thought, anyway.