Comment 3 for bug 1667709

You mean you don't want kittens peeping through bits of your window? You monster! :-D

Okay, so I'm fairly certain you got bitten by zesty having 3.22 gtk. Gnome, in their infinite (and absolutely always correct) wisdom decided to change CSS handling in gtk 3.20, breaking applications that were using the class to assign styling. From 3.20 it only works with node names. We actually already have a fix in http://bazaar.launchpad.net/~gnome-terminator/terminator/gtk3/revision/1714 but you are ~10 revisions behind. You could enable the nightly gtk3 PPA found at https://code.launchpad.net/~gnome-terminator/+archive/ubuntu/nightly-gtk3 which will get you all the latest fixes.

Be aware that rev 1714 is only a partial fix, as the theme specific fixes and styling are very likely also broken. It looks like you are using the Ambiance theme by the styling of the tabs in your image, but with Ambiance you *should* see tabs that look like the ones in gnome-terminal if you have the "Extra Styling" checked in Preferences.

I cannot see this issue (I'm on gtk 3.18) so I'm rather reliant on someone being willing to either fix these themselves, or be prepared to do a frequent and quick feedback loop, being my eyes while I make changes.