Stop wasting alt-click

On desktop, “alt-click” is a massive affordance, it's easy to reach and can be used quickly and frequently.

And it's currently being wasted on marking a comment unread, something which probably happens on the order of never.

It would be a lot more useful — especially for administrators and mods — if alt-click selected comment, and allowed performing bulk-operations e.g. moving a bunch of comments to a new thread, or reporting or deleting them, operations which are currently respectively impossible, tedious, and tedious.