Jacob, the Reply button works for fine me in that thread, both in Firefox/Mac and Safari/Win.
Now it works for me, too.
Thank you very much for your intervention, Claudio.
Somehow I am back to being unable to answer in that thread again.
For a while I have tried in vain to post a reply to Claudio, and alternatively to the OP.
The OP has given a rather strange answer to Carlos.
I don’t see any issue with your account or with that thread.
Thank you for looking into this, John.
I believe there is something rather strange going on in Firefox:
First I was unable to post so I posted here;
then I was able to, and posted here;
then I was unable to again, and posted here again, and found out that I was unable to post in another thread, to;
then I opened a new Firefox window and was able to post in both threads.
I am still unable to post in the original Firefox window which has 8 tabs open.
I believe I shall just have to close it.