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: Several small updates, mostly to clean things up a bit, and align property names and such.
NAME - I think you're wrong: my understanding (and also the way the text is written - otherwise we'd have to change it in the API draft) was that Connection Properties can (and should) also be set on Preconnections, to give as much input as possible for Connection establishment. In the API draft, the Selection Properties in Section 5.2 can only be used on Preconnections: you can't ask for congestion control after establishment. You can't say that you'd rather have multistreaming support after establishment. But that doesn't exclude Connection properties from being usable earlier. Required minimum checksum coverage could influence choosing UDP-Lite vs. UDP. Bounds on Send or Receive Rate could influence the interface choice. The capacity profile could influence various things (and no, there isn't a matching Selection Property now - there is a per-Message override). So... I think that either you're wrong, or I'm missing something and the API draft heavily lags behind a decision that was made. I hope not!
NAME The API drafts says: I interpret this as only the Selection Properties influence selection and the Connection properties are used to further configure the connections according to user preferences. Otherwise what is the difference between them?
If you interpret it as you do, I think the text isn't clear enough (indeed it isn't super clear - in particular, "eventually established" is misleading IMO). Though, note that it says that Connection properties can also be used later. Regarding the difference between them: Selection Properties only make sense for Preconnections.
NAME - sorry lost this thread. But I saw that you have started cleaning up some Connection properties that had mixed Connection and Selection properties up in the API draft. Does it mean that we are now in synch and agree that only Selection properties are used in the selection and Connection properties are used for configuration (both during establisment and also after the connection setup).
NAME the other PR means nothing about what I said here: it only tried to address issue which is about a wording inconsistency in a specific property. You say that Connection properties can also be used during establishment - if you agree with allowing this, then why not allow to configure them as early as possible and allow them to influence selection?