I did reproduce this behavior successfully with right-click and paste. I also reproduced it with the "paste" option in the Edit menu; that produces even more coolness by failing to trigger both the keyboard and mouse handlers, which are required to clear the "type or paste a question link or numeric question id" text, producing the following result:
It seems that these paste methods are not properly supported, you're right.
That said, it seems that neither the Stack Exchange developers, the testers, nor other users have had a significant problem with this limitation in the past three years. We could try to detect this mose activity, but may I suggest keeping one hand on the keyboard? Using ctrl-x, ctrl-c, and ctrl-v (or cmd-x etc, if you're on a Mac) is much more efficient.
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