Ken,
I usually (and did) log into Member Section from the A-D Home Page, then scroll down to check Forum at the page bottom and then select a topic, then the specific entry to edit. Many of my Events entries are necessarily long and consume time to enter, then Preview. This failure episode was a first for me.
I can't really import from Notepad, etc because I sequence new events by dates between already entered dates, and I initially tail a new one onto a just prior date entry to pick up the bolding and color, which I use on all my entries for better legibility with my old eyes, even though I still correct to 20/20, (old eyes need more light). When editing an Event after a period of being shown, I then do a new Reply to the edited Event with the Dates, Cities only; otherwise no one knows of the new added material.
As to the Forum log-in question, the few times I have done that, I always check "Log me in automatically each visit" and have never found that to work or of value-despite checking it. It does NOT require me to relog in again after doing that, to answer your question.
The fact John has experienced my problem several times suggests a bug. Again, this was a first for me. Thank you both for your answers.