I don't think pidgin dwarven is the way to go at all. Assuming that the [UTTERANCES] tag implies the vocal cords of the creature are unable to vocalize the words of the non-utterances tag then it is simply biologically impossible for kobolds to speak dwarvish and indeed vica versa.
(I'm currently reading a book where an evolved-from-canine-ancestors species is talking 'growled English' to the human characters (and other the other homonids, who are the ones who taught the canids, having picked it up themselves and usef it as
their Lingua Franca, which is a bit of a stretch that I hope gets explained later!). Anyway... One has to imagine that even with 'utterances' (that I've never presumed to mean anything other than the tendency to be mumbly and/or sound like intejections, possibly Turets-like), it is possible for a
suitable voice modulation to be possible, even if not all phonemes are possible. Thus vocabulary might be artificially constrained. The big hurdle, then, is the brain being capable of language of
any kind, and the this does not have to be related to the
ability to vocalise. So, yes, it could be sign-language, but pidgin/reduced-vocabulary language is there as an option. But I'm not welded to it.)
The less of a concept of property there is, the stronger society is, so from a societal strongpoint the mystery is backwards; how do the societies of creatures with a strong concept of private property simply not dissolve altogether?
This kind of "no common reference" is the kind of stumbling block we may, in fact, be seeing. Like the society of reptilian-descended beings one might encounter in sci-fi, their practice of minimal care for their young (or total lack of it, beyond precautions to keep the initial clutch of eggs safe) seems to end up in a society with no concept of family - perhaps flexible fealty to a 'tribe of effective orphans' - and thus social standards that we find difficult to understand (and they, likewise, with our social setup).
The thing here is that, being thieves kobolds will generally end up with a lot of surplus junk they have stolen but which they have no real interest in.
What you say is possible, but I'm challenging the concept that they are 'thieves' outside of our own moral-relativism. Redistribution of items (for whatever purpose... perhaps some racial fear of too many like things being stacked on top of one another, they need to be 'smeared out a bit', items strewn across a site or taken to yet another site altogether, lest it annoy the kobold gods..?) is theft to
us, but not to them. And our practice (even in the semi-communistic system of settlement we currently 'enjoy') may be seen as something that the
kobolds have to learn to reinterpret as no longer an anathema to their own relative morals...
Yes, Toady uses stuff like [UTTERANCES] and [THIEF] in has raws, but what does Toady know? He not smart like kobold. He just dumb human with dumb human 'standing of how universe
really built!