Change:
efficiency and convenience for the application, since the Transport Services system can automatically optimize behavior. <del> There are several reasons, however, that an application might want to explicitly isolate some Connections.  These reasons include: </del> <ins> The Transport Services API can allow applications to explicitly define Connection Contexts that force separation of Cached State and Protocol Stacks.  For example, a web browser application could use Connection Contexts with separate caches when implementing different tabs.  Possible reasons to isolate Connections using separate Connection Contexts include: </ins> Privacy concerns about re-using cached protocol state that can <del> lead to linkability.  Sensitive state may include TLS session state RFC8446 and HTTP cookies RFC6265. </del> <ins> lead to linkability.  Sensitive state could include TLS session state RFC8446 and HTTP cookies RFC6265.  These concerns could be addressed using Connection Contexts with separate caches, such as for different browser tabs. </ins> Privacy concerns about allowing Connections to multiplex together, which can tell a Remote Endpoint that all of the Connections are <del> coming from the same application (for example, when Connections are multiplexed HTTP/2 or QUIC streams). Performance concerns about Connections introducing head-of-line blocking due to multiplexing or needing to share state on a single thread. The Transport Services API can allow applications to explicitly define Connection Contexts that force separation of Cached State and Protocol Stacks.  For example, a web browser application might use Connection Contexts with separate caches for different tabs in the browser to decrease linkability. </del> <ins> coming from the same application.  Using Connection Contexts avoids the Connections being multiplexed in a HTTP/2 or QUIC stream. </ins> 5.

Discussion:
Addressed MW comments; and also tidied several successive similar examples into one para.
Section 4.2.3, item 3: "Performance concerns about Connections introducing head-of-line blocking due to multiplexing or needing to share state on a single thread." I don't think application programmers should decide against using functions such as Connection Grouping because they try to optimize their performance in this way. If it performs poorly, the Transport Services system shouldn't do it. I know this isn't always black and white... I'm guessing that this was written with HTTP/2 in mind. Still ... if a mechanism is judged as generally performing better most of the time, the system should probably use it. If it doesn't perform better e.g. depending on the length of transfers, which may be known from HTTP header, then maybe the Transport Services system is the ideal place to dynamically make such a decision? Anyway - I don't think that we should indirectly suggest to application writers that internal functions chosen by the Transport Services system on the basis of high-level information like "these Connections belong together" might in fact perform poorly, and hence they may be better off not using them if they want the best performance for their application. So, I would remove this item.
Sure, applications might do many things and some decisions to multiplex multiple flows using a single protocol instantiation might be less performance, however, I would suggest removing this bullet: " * Performance concerns about Connections introducing head-of-line blocking due to multiplexing or needing to share state on a single thread.", because I think it creates confusion as Michael suggests. A developer understanding complex tradeoffs (such as web client browsers or NFS/SMB servers) will consider this anyway, others should not be worried.