A Thief in stealth is not affected by knockback, more specifically a thief that is finishing a downed ally while in stealth is not affected by the engineer skill magnetic inversion which is a skill used to push back all nearby foes.
I have tested this situation multiple times and magnetic inversion fails to interrupt every time.
I expect that since thiefs are able to be damaged by area of effect skills they will also be able to suffer the other penalties of them such as knockback, and since thieves are not invulnerable or absent from their current position only unable to be seen or targeted, they should not be an exception to the rules.
This bug gives theives a great advantage when finishing a downed player while invisible.
Correction, a thief is able to get knockbacked. Often i am feeling like a pinball going from left to right to left again. So no, don’t think it’s a bug. Bug is more that as a thief you are getting pinballed all the time.
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