Code change:
support removing a Message from its buffer, this property may be ignored. <del> Niceness: this represents the ability to de-prioritize a Message in favor of other Messages.  This can be implemented by the system re-ordering Messages that have yet to be handed to the Protocol Stack, or by giving relative priority hints to protocols that support priorities per Message.  For example, an implementation of HTTP/2 could choose to send Messages of different niceness on streams of different priority. </del> <ins> Priority: this represents the ability to prioritize a Message over other Messages.  This can be implemented by the system re-ordering Messages that have yet to be handed to the Protocol Stack, or by giving relative priority hints to protocols that support priorities per Message.  For example, an implementation of HTTP/2 could choose to send Messages of different Priority on streams of different priority. </ins> Ordered: when this is false, it disables the requirement of in- order-delivery for protocols that support configurable ordering.

Related discussion:
text: What's bad about having more information available that can guide the selection process?
NAME the problem is that the Connection properties are not expressed in a way suitable for selection. If they should also be used for Selection they would have to be reworked to be of type Preference. Otherwise I do not know what they mean for selection. What does it mean if I pick say a particular connection group transmission scheduler? Is it required or preferred? Most connection properties also do not look very useful to me for selection so in case there are some we need I think it would be simpler to just define a matching selection property.
NAME we're only discussing whether it's allowed to use them as additional input or not. I agree, some (like the scheduler choice) don't seem useful, but some do... generally we may not have good guidance on how they should be used by an implementation, but giving the system freedom to use as many inputs as possible is probably a good thing. Regarding the type, require/prefer//ignore/avoid/prohibit obviously works fine for a "wishlist" of boolean character: having something, or not having it. The selection properties are generally like that - except "Interface Instance or Type" and "Provisioning Domain Instance or Type" which are, well... wishlist-collections. Consider the capacity profile. Surely configuring this early can be useful input - e.g. if someone picks low latency / interactive, you may even want to put this traffic on a specific network interface! But if you'd want to make a copy of the capacity profile as a "proper" selection property, how would you do it? Apply require/prefer/ignore/avoid/prohibit for each of its values? Then I could say "prefer" low latency/non-interactive but "avoid" low latency/non-interactive, which would surely be odd. Apply the qualifier to the whole thing? Then it's about, e.g. "avoiding" to use a capacity profile at all. That's odd as well. I think it's in the nature of the current selection properties that they merely say "I want to be able to do this, and this is how important it is to me", which is different from configuring something. That's also why, as written, they simply wouldn't work for later connection configuration.