Just curious!
Hm. I’m not sure. There have been several follow-up columns in the last year taken from posts in “Comments on Cecil’s Column.”
The thing is that most questions posted in GQ get answered, and answered well, by the Teeming Millions. Hence, Cecil wouldn’t have any need to add more. That’s not to say he wouldn’t ever – just that he doesn’t usually tend to pay as much attention to GQ.
Perhaps someone with some time on their hands (unemployed, under-employed, students on holiday, etc) could research.
Of course We The Teeming Millions answer them well 
Has he ever though, I wonder?
Yeah. Like I got too damn much time on my hands:
1 June 2003 GQ post by Lint6: Why doesn’t .9999~ = 1?
11 July 2003 Column: An infinite question: why doesn’t .999~ = 1?
Youuuu raaannngg?
The list of columns has links to the most recent, and it was only a month ago that Star Was was said to have submitted Remembering the Alamo (and the death of Davy Crockett) via the SDMB, but that was from Comments on Cecil’s Columns. The same with clarke’s More on Memes: The Teeming Millions lose their minds.
Most of the columns say they were submitted “via e-mail” or “via the Internet”, which didn’t mean much to me until I walked back to the first column of the year, and found that Cecil had fielded a question about Napolean’s penis from someone (not a doper) named MudGirl, via the Internet. I stopped right there. Some questions are best left unanswered.
O no!
Question posed by Lint6, in GQ, on 06-01-2003: Why doesn’t .9999~ = 1?
Answered by Cecil on 11-Jul-03: An infinite question: Why doesn’t .999~ = 1?