To me that is acceptable, of course. It's part of personal RP, and the actual exersize of roleplaying and interactive storytelling. A character should not be "me, if I happened to be born in X place in the EVE cluster and grew up with a different history" - ie, they shouldn't be speaking with the player's voice saying things that are relative to their setting.
To compare, Arista has a lot of mannerisms I have to consciously remember to use beyond the stereotypical 'Amarrian proper' a lot of the Amarr bloc does, because she's a) from the Kingdom and b) should have habits / behaviors from her own planet. (if i cant 'get into character' with all of them, I simply don't RP, because for Reasons she must always be eerily consistent in her behavior.)
I mean as a simple example even on a single planet things are different dependent on local society; the noise that someone in the US makes that is a sound of agreement ("mm-hmm") is different than someone from the UK (a brief "mm.")
Ari does that crap:
* Arista Shahni hums in thought.
* Arista Shahni hums in agreement.
Of course the reader can't HEAR those, but I basically added that non verbal vocalisation and communication is common where she comes from, so she does a lot of it.
So for Synthia to have predetermined mannerism is not only normal, it makes logical sense that a programmed AI would be programmed to follow some form of "traditional human social protocol".