Because we need to identify malicious behavior.
(This just broke one of my bots.)
Are the details of this policy discussed anywhere?
I don't know. Probably. We always told people to specify User-Agent, just the check
Is it permissible to send
thus providing precisely the same amount of information as if not
supplying the header at all?
No, you clearly miss very simple idea that with such user-agent you clearly identify
yourself as malicious, whereas when you don't specify, you're either malicious or
Do note, we're good at detecting spoofed user-agents too, so if your bots disguise as
MSIE or Firefox or any other regular browser, your behavior is seen as malicious.
We do not like malicious behavior.