Once upon a time, the guidance from the compiler optimizer team was to never use noexcept except where the standard required it, because applying noexcept prevented functions from being optimized in many cases. Sometime around 2017 the compiler was fixed to play nicely with noexcept, and the new guidance is to strengthen noexcept wherever possible because deeply strengthened noexcept avoids emitting enforcement code in debug builds.

Before we have full testing out in GitHub we want to restrict this to "blindingly obvious" cases; so most conditionally noexcept cases should wait for now.