ok, so I've done a bit of digging and found a bug for one place;
If the "Editor" option for the field is set to None, and the contents of the field are "plain text" then it behaves as you describe.
I have fixed it for the 20.22 build
You can change it in your netweb.clw by changing line circa 6577 from
if instring('readonly',p_status,1,1) and (p_display = Net:Web:HtmlOk or p_editor)
to
if instring('readonly',p_status,1,1) and (p_display = Net:Web:HtmlOk or p_editor > net:HTMLNone)
Cheers
Bruce