It would be very nice if an icon of sorts was shown when a release has been added to your collection. Maybe next to the bookmark icon?

For those with large collections and small memories, it would be a nice visual indicator. Normally, the only way to know if something is in your collection is trying to add the release to your collection again or looking through the actual collection list.

I don't know how feasible this would be, but I think it would be a nice feature for those that use the site as reference as well as a cataloging tool.

I'm going to add my weight onto this and say I'd like to see this too. I've been wondering the same for a while, especially on artist pages with many releases.