If you have tried to leave a comment on this blog and it didn’t work, I apologise.
Two days ago I found out that commenting was working properly only if you were signed in (e.g. with 
or 
or 
) or if you were using an https:// URL (which has its own bug). Otherwise, the “Send” button either did nothing or in some cases displayed a “wrong Captcha code” error message even though you had entered the correct code.
I haven’t been able to find the root cause of the problem. I presume it is related to the wpDiscuz plug-in which I use to handle comments.
Yesterday I disabled the Captcha feature, which seems to have fixed the problem. As a bonus, that also lowers the barrier to leaving a comment. I have other spam protection measures in place. If those prove insufficient I’ll revisit the decision.
Thanks to R for reporting the problem.