target blank only for posts?

Yes, it should work for the posts and all comments (reactions) on your posts.

Sorry, but I did not understad. It works only for posts not for comments. Links in comments have only “nofollow” without “target blank”.

Do you have an example/url?

Here you are https://egor.life-trip.ru/test-post/

Did you check my url?

Yes I see. It’s very odd.
The only explanation I can think of is that somehow the WordPress filter get_comment_text is not used by your theme.

Could you check if it does work with one of the default themes? (like Twenty Fiftheen) Just to make sure if that’s the cause.

I tried to install Twenty Twelve and I have the same problem. There are no target blank in comment.

P.S. I tried to deactivate all plugins.

OK, thanks for trying.
And does it work when you check “All contents”?

Yes, If I check “All contents” it works in Twenty Twelve theme.