> The meaning of the specified machine-readable version should be the version in which the code has been marked as deprecated.

+1

> In an ideal world, of course, the `@deprecated` tag would support two machine-readable values

I disagree that a second version number needs explicit support. Deprecated doesn't just mean that code *might* be removed, as the PSR-5 description suggests: it may be discouraged from use for [other reasons](http://en.wikipedia.org/wiki/Deprecation#Reasons_for_deprecation) too. Of course, any second version number should be read as part of the tag description, and that can be used for whatever purpose is desired on a project.