I disagree with the idea of "too late" in most cases, especially software. All that's required is sufficiently advanced warning. Perhaps the docs could say, "Will be changed to the WM_MENTERTEXT message starting in version 7.5; use '/say' to obtain the current behavior."
Furthermore, as the interaction occurs entirely numerically, the value of the constant can be left the same, and merely the name changed, interfering only with readability of legacy code and no functionality whatsoever. Then the proper WM_MCOMMAND could be added as WM_USER + 202.
But yes, the docs could be much clearer regardless, in that entry, and the rest of the docs overall. Let me know if I'm beating a proverbial dead horse here.
