My intuition that lying is significantly different from some other forms of deception is driven by an intuition I have about speech being special vis-à-vis the virtue of honesty.
Consider: "She told us she is going to go to Cracow, and she is an utterly honest person, so even though we are her enemies, we can rely on her going to some city named Cracow at least at some point in the future." This seems a reasonable thing to say.
But consider: "Her footprints at this intersection lead to Cracow. She is an utterly honest person, so she must be going to Cracow." That is surely mistaken reasoning. It is not a sign of dishonesty that one lays a false trail, unless one has promised (implicitly or explicitly) not to do so.
The tie with promises seems significant to me. An honest person only makes promises that she intends to keep.
Now, let us suppose that George prefaces every assertion with: "I promise that I will now only say something sincere." That would be dreadfully annoying (there are characters in fiction who do this kind of thing). Part of the reason for the annoyance is that it is quite unnecessary. The commitment to speak only sincerely is already there in the assertion that follows the preface.
As our Savior told us, our yeas should be yeas, and our nays, nays. Nothing more is needed, because our yeas and nays already include a commitment to speak sincerely. This commitment is part and parcel of making an assertion rather than musing out-loud, asking a question, making a promise, quoting a line of poetry, etc. Indeed, much or even all of what distinguishes an assertion from other speech acts is precisely this commitment to speak only the truth. (Actors on stage do not make assertions or promises.)
Granted, sometimes we emphatically do promise to speak the truth in some matter. I think that is not a sign that we ordinarily have no such commitment. Rather, the promise is a moral-gravity booster, in the way in which making an oath is a legal-gravity booster (if one speaks falsely under oath, one commits perjury, instead of merely hampering an investigation, etc.) One could similarly boost the moral gravity of ordinary promises by promising to keep the promise. To boost the moral gravity of an obligation is simply to bring it about that it would be a greater offense to go against the obligation.
If I am right that asserting p is normatively equivalent to promising to say only the truth or maybe to say only something one believes and then saying a sentence that expresses p, and if I am right that an honest person does not make promises she does not intend to keep, then an honest person does not lie. But various non-linguistic kinds of deceit involve no commitment, explicit or implicit, for the deceiver to be breaking, and hence under some circumstances will be compatible with honesty.