deletebah non (I agree with the reason, and I also agree for hmm yes or hmm no, of course).
keepque si: this phrase must be defined to be understood, it must be kept, this is obvious.
I would also keep mais si, which means si, but with more intensity, and more spontaneously. This use of mais is not obvious at all. It's possible with other sentences as well but I think that, in mais si or mais non, adding mais also has the additional effect of being more polite, omitting it might seem rude in some cases. It's clearly a set phrase, just like au revoir. Lmaltier 22:13, 5 December 2009 (UTC)
Que si failed RFV, which is just impossible because it's really common. But I still don't think it's idiomatic (but yes!) Mglovesfun (talk) 22:30, 5 December 2009 (UTC)
To find uses of this sense, add oh to the search. 1 900 000 Google hits for "oh que si"! Lmaltier 09:18, 6 December 2009 (UTC)
I was the personal that nominated it for deletion! Mglovesfun (talk) 18:52, 9 December 2009 (UTC)
Oh! Confusing. I didn't see this discussion until after I had deleted [[que si]] for failing RFV; so I thought you were listing it here to get it undeleted. But I now see that you had listed it here a few hours before I deleted it. —RuakhTALK 19:17, 9 December 2009 (UTC)
Well, in a French mind, que si certainly does not mean que + si. A French sentence cannot be composed of que + a single word, except in these 3 set phrases: que si, que oui, que non. Lmaltier 12:19, 12 December 2009 (UTC)
Well, what does it mean? I can't tell you other than "que + si". Mglovesfun (talk) 12:24, 12 December 2009 (UTC)
If you interpret it this way, then que si does not mean anything, because it's not normally possible to use a sentence composed of que + a single word. All Que ... sentences have a meaning only if they include a verb. These are the only exceptions I can find (with que nenni and que dalle). Lmaltier 16:11, 12 December 2009 (UTC)
Ironically, the first two should definitely go, but que si is more debatable as Lmaltier says, I see no reason to restore it but I can see why others might want to. Mglovesfun (talk) 18:25, 14 December 2009 (UTC)
Although these pairs of words are very common, they seem to mean nothing more than the sum of their parts. I would vote for deletion. BedfordLibrary 14:55, 3 August 2010 (UTC)
Deleted [[bah non]]. I don't see any discussion above clearly about [[mais oui]], so haven't deleted it.—msh210℠ (talk) 17:21, 31 August 2010 (UTC)