Double quotes parser style “ ” ? ”

Hi,

Sorry for poor topic title – that reason I can’t find it in search engines.

I have two another websites builded on TwentyFourteen and TwentyFifteen.

When I write:

This is something “nice”.

in visual editor,

I got it parsed on website (copied directly with Inspect element, no CSS there) as following.

TwentyFourteen:

This is something “nice”.

TwentyFifteen:

This is something ?nice”.

And I would get TwentyFifteen result in TwentyFourteen, as this is the correct one for my language – Polish.
I searched in language files and with AstroGrep program, but found nothing.

Any ideas?

Thanks in advance,
Greetings