Ai team believes everyone uses English it feels like.
Backtick is reported to fail to work often, but here it’s even more convoluted.
In Russian, the key that houses backtick (`) and the tilde (~, with Shift held) types Cyrillic 'ё' and its capital from 'Ё' respectively.

If I map Curvature Tool to just backtick — it works.
But with Shift added, like Ai offers by default — nope.

There is a larger request on a similar topic, Some shortcuts don't work while using non-English keyboard / language layout — http://illustrator.uservoice.com/forums/601447/suggestions/44393445 — but perhaps the team needs to solve it one case by one?

In this case — here is another related problem with Russian: Color / Gradient / None key under the Fill / Stroke selector are mapped to these keys , . / (comma, period, slash) in a 'standard' layout, but in Russian work as бю. (two Cyrillic letters and period)... so this makes None key work as Gradient with Russian input — and it’s infuriating. Here the position of the key matters, and not the symbol on it!