I've been on this list for a while, but I am not very active and I'm definitively NOT a PREMIS-expert, which my comments may reflect.
> recommend for Events and Rights that only one is used if possible. It would possibly introduce unattractive levels of complexity if it is recommended to use as many identifiers as an institutions wishes.
The »Rights» question is maybe a bit complicated. Different rights may apply in different countries. Furthermore: Rights have some connections to the concept of license (which does not only apply within software development), and one work may have several licenses: three or four licenses are not uncommon.
> the theory that it is better to prescribe an exact order than to allow random order - easier for the recipient of the record to process the record if the ordering of the elements is known. You can debate the validity of this theory, but it was a fairly well-accepted theory "back in the day"
Particularly: It is easier for the recipient if the recipient is a human, who, for some reason needs to edit the serialization "by hand".