I can't reproduce this in Chrome. Here is dropdown scrolling:

https://www.dropbox.com/s/0ydi3ahiuvtbmc4/filters%20scroll.swf?dl=0

Maybe this is a compatibility bug?

You can already copy test cases in "Test suite edit" view by clicking on the yellow icon next to each test case

Currently it's not possible but I'm leaving this open so that other users can vote for this idea and if there's enough interest we'll do it.

This is not very clear. Closing.

You can do this by clicking on "Filtering" above the bug list, selecting "Assignee" as your filter and selecting everyone but you in the list.

It is not currently possible to invite users via the API