Please read the guidelines[0] and FAQ[1]:
> Why can't I post a comment to a thread?
> Threads are closed to new comments after two weeks, or if the submission has been killed by software, moderators, or user flags.
> Why can't I post a comment to a thread?
> Threads are closed to new comments after two weeks, or if the submission has been killed by software, moderators, or user flags.
I question the wisdom of this limitation in monthly recurring threads. I think it should be special-cased for those specific instances.