Some (rather lot) text application uses archivation to decrease file size. For example: file.abw.gz file.pdf.gz file.fb2.zip By default all archive types (.gz, .zip, /etc), independently on second level extension, are associated with xfce-extra/thunar-archive-plugin. It will be good to make it possible to set an application, invoked by thunar, depending on second level extension. I.e. for listed example: For file.abw.gz thunar should invoke AbiWord, for file.pdf.gz --- selected pdf viewer (in my case evince opened such file normally) and for file.fb2.zip --- selected ebook viewer (for example, in my case, CoolReader3). For the rest applications (for which second level extension is not present or unknown --- default application for the first level extension, i.e. --- xfce-extra/thunar-archive-plugin.
The missed one: Also it will be good to make assotioation for files with no extension (and/or unknown one). In my case such files are text ones, so should be opened with favourite text exitor (usually gvim).
Except man pages and stuff in /usr/share/doc, I haven't met such files. Therefore closing won't fix. Reopen if you can provide a patch.