There are 2 comment fields - even MP3diags shows 2 fields COMM, each with the size 6 for the file exported by Audacity.
Yet, for the files exported by Audacity, the first COMM field has no language token, whereas the second field has the languge token XXX.
Editing the file with MP3tag changes both to ENG.

So, my
Audacity causes problems.
If your windows does not display the comments at all, check if ENG is the best setting or whether XXX would be better.