So explain to me again why kobold PCs lack darkvision, when other kobolds have it, if it's not "balance."
Because it was in the MM, released when they were still feeling out the power of certain abilities, and felt limiting it was useful for balance - and if they were to write the rules for that race at the current point in time, with what they have learned in the interim, they would almost certainly give the kobold PCs darkvision.
Here's my question - what other examples of this PC/NPC dichotomy actually bug you? The kobold darkvision one was really the only one that got to me, since it changed a fundamental element of the race. But as mentioned - it is also something they probably wouldn't do now, and it was pretty much a solitary example.
Yes, lots of other monster races are different from the NPC/PC versions... in ways that are completely irrelevant to the core of the race itself. A PC minotaur feels like a minotaur, despite not operating identically to a minotaur monster.
So, are there any other cases that actually come to mind of this being a problem, or were kobolds it? Cause if so, I don't think you have anything to worry about, since that 'issue' will likely be fixed whenever they have an offical PC race.