[DiapDealer]

Let's check around a bit to be sure. Someone may be using a batch file to automatically open HTML or Text files in Sigil for some reason. I can't see what the advantage might be myself.

I'm also imagining both the Open HTML and the Open Text file options have been broken in this regard for quite some time. Neither would have any logic to let Sigil know if it should be handled as an epub2 or an epub3. Which I believe has been mandatory info for a lot of Sigil's functionality for a few years now.

I just checked and we ARE still registering Sigil as a candidate for opening .htm|.html|.xhtml files with the Windows installer (but not .txt files). Easy enough to remedy, but I just want to make sure we're not overlooking some sort of use-case.