The title says all. This I have been wondering for some time. I assume the answer is no; else I suppose I would have noticed him.
(I hope I do not break any rules by asking this.)
don's personal presence on the internet is essentially limited to his web pages at stanford.
on his tex page he lists a contact for reporting "purported errors". this still happens to be me, although the duty was officially turned over to karl berry as of 1 january 2015.
as don has said many times, he does not have an e-mail address; he relies on the good offices of a secretary to communicate urgent messages. his next scheduled tex review is in 2020, and he won't even look at tex and friends (except as a user, for his own work) until then.
There is an even better answer listed on his web pages, more specifically, on the page answering the FAQ question ‘So you’ve retired?’:
The only way to gain enough efficiency to complete The Art of Computer Programming is to operate in batch mode, concentrating intensively and uninterruptedly on one subject at a time, rather than swapping a number of topics in and out of my head.
This unambiguously means that unless he’s working on a TeX chapter right now (which I’m assuming to not be the case just by a stochastic estimate) he will be buried very deeply into a subject that is not TeX and therefore see no time to answer any TeX questions as interesting as they may seem.
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; maybe\hbox
or\vbox
, but\phantom
works.