Crash reports require a copy of factorio-current.log. Many users do not have a program set up to view this file, so they try to attach it directly. And the forum rejects it.
Allowing the .log extension on attachments will make bug reporting easier for everyone.
[fixed] Allow .log extension
Re: Allow .log extension
makes sense
Re: Allow .log extension
While it makes sense, it also always makes sense to compress down log files.
Re: Allow .log extension
I finally managed to find the option used to enable it 
It is now possible to upload log (and ini, txt, cpp and few more) files.
It is now possible to upload log (and ini, txt, cpp and few more) files.