Pasting into composer address box can lose spaces
I often end up building a list of recipients from something like a maintainers file, and pasting them into the To: or Cc: box of a composer window.
When the box gets full, and the cursor is at the right-hand side, pasting with the middle mouse button will remove all the spaces.
In this example we pretend I'm just sending lots of copies to myself (yes I know it wouldn't actually do that), select my address and repeatedly middle-click...