Thank you, Fletcher, for your swift answer.
I have accounts in both websites I mentioned below.
In both, you cannot send the text of a new discussion after logging in, without choosing the category to which the discussion belongs. But the drop-down menu for categories (also in a screenshot I sent you) is empty.
So I tried contacting you by clicking on your «support» button (in the other screenshot), but that button does not have any hyperlink behind it.
These are minor hickups, but generally, I am happy that your resurected MultiMarkdown (as Composer Pro v4, and soon v5) is so successful. In my opinion, it is surely a well-deserved success.
Only, I thought nobody should be prevented from participating (along the whole spectrum activity ↔︎ pasivity) to this undertaking. That's why I drew your attention to those defects in both your websites.