As I was going about my business commenting on Blogger with Firefox
(instead of Chrome) I came across a page that told me
'it seems you have third party cookies blocked'.
So I changed that one setting so I could continue.
Of course, I was curious about Chrome and wondered if that could be my
problem there. I checked and, sure enough, all was well with
my Google account using chrome again.
Weird. I have no idea why the setting would have changed, but I guess
that doesn't matter. What DOES matter is that I can comment
like usual. Yay.
I'm posting this just in case it could help someone else with the same problem.