I should have added, by way of explanation, that you only get the wrong settings, and unexpectedly see the format changes, if you've never set any options yourself.

There are only a few of us using the add-on (you're only the third who has admitted it) - about 5 on Firefox and 5 on Chrome, who may be the same five. The only thing I know, from the Firefox statistics, is that most are in the UK and one is Czech - or at least using a Czech version of Firefox. Maybe any users in the US are more likely to use Chrome.

The reformatting, which Richard described, is the one thing that does not work in the new Chromium Edge browser. The main features - locating new posts, one-click linkifying - all seem to work.

The full list of features is given under About this extension on the Firefox Addon page.
The Chrome version, which also works-ish in Chromium Edge, is here.

If you try the Firefox version, you may want to set the options as I described above.

The support thread on Mudcat, for questions or observations, is here. I usually post there about new versions but I thought - well, nothing's changed, nobody will notice ...