On Fri, 18 Dec 2015, gregrwm wrote:

> it may well be that sort behaves in accordance with the definition, if 
> so i say the definition has a bug.  "a" should not preceed null.

What it said was that when the extension begins with a number, as in .7z 
or .9 (which was your example), then there is no definition.

I agree that seems ridiculous.  It obviously is doing something and what 
it is doing makes no sense to me.  Why should -V give unpredictable 
results under any conditions?  Apparently, that was their plan.  If you 
write to the developers, let us know what they say.

REPORTING BUGS
    Report sort bugs to bug-coreutils at gnu.org
    GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
    General help using GNU software: <http://www.gnu.org/gethelp/>
    Report sort translation bugs to <http://translationproject.org/team/>

Mike