Names in brackets
Well, the point is, I don't know. Most languages are listed in boldface, but some are listed in normal typeface and in brackets. I did not do that, and I do not know who did it why. My guess is, that brackets are ued to denote a specific variant under a macrolanguage, or a dialect (according to ethnologue) of a language which is also a dialect group. But I am not sure, and for the ones I entered, I did not follow this trait because I was not sure about it.
OK, now I get the point of the question. Having looked at the three entries in brackets, it appears they were put in by Jon Harald Soby, and indicate dialects/languages having ISO 639-3 codes but no ISO 639-1 codes. I agree with you that if the page uses special markings then we need a key to these in the introduction. Exactly how much information this page should be carrying is another question, related to the question of whose benefit the page is designed for, and it seems to me that these will need to be addressed sooner rather than later. So I'll start yet another thread on that.