OK, I give up, multiquote is bugged … I will say that I am not fond of the new skin, but I can deal with that - I just hate when actual functionality is hosed up.
How specifically is it bugged?
If you click on the words MultiQuote, it doesn’t work, even though it looks like a clickable link.
If you click on the symbol next to the words, it works. At least, that’s been my experience. So multiquote still works, but in a non-intuitive and misleading way.
Click the icon next to “Multi Quote,” and it will change from a plus sign to a pair of quotation marks. Then quote the next poster (Reply With Quote) and both quotes will show in the reply box. You can do this multiple times for adding additional quotes.
So it’s not a bug, it’s a feature. 
I am unable to test this on the creator’s webpage because he apparently doesn’t have multi-quote active.
Multi-quote is in fact a feature. You click on it for all the posts you want to quote - these need not be consecutive. Quotation marks are superimposed over the adjacent icon. Then, in the last such post, you click on “Reply with Quote.” This opens a reply box with all selected threads quoted.
There IS a bug, though - clicking on the words “Multi-Quote” should select the post, not just clicking on the icon. Noted in my next round of bug fixes at:
http://boards.straightdope.com/sdmb/showpost.php?p=20472165&postcount=291
To avoid confusion, I’m closing this thread. Please post requests for bug fixes in this thread:
http://boards.straightdope.com/sdmb/showthread.php?t=835598&page=6