Great thread - thanks.
Originally the 'reputation' system on Invision allowed users to increase or decrease a users reputation, as well as leave comments. This was disabled immediately as we could see that the system would not be taken seriously and people would misuse it. However, the latest version of Invision has a cool new addon which allows for a simple 'like' button as you have suggested, doesnt allow negatives or comments. Brilliant! I have enabled it and 'liked' your post already.
Yes! The @name addon is one I want also. It would be really beneficial to be notified when your name has been mentioned. This is on my list and there is likely already a plugin for it which means I'll get it installed today or over the weekend.
Thanks Jeremy!