If you're using a Unix version of AbiWord, you can also use the File->Open
dialog, and select the file in the list, but then force it to open it
as Text by choosing that format from the file-type list. That selection
will override the extension. I don't think this is possible with Windows
(without the file contents detection you describe) because of the way its
dialogs have a 1:1 correspondence between type and extension.
-- Shaw Terwilliger