One of the downsides of converting positional-only functions to Argument Clinic is that it can result in misleading docstring signatures. Example:

socket.getservbyname(servicename[, protocolname])

socket.getservbyname(servicename, protocolname=None)

The problem with the new signature is that it indicates passing None for protocolname is the same as omitting it (the other, much larger problem is that it falsely indicates keyword compatibility, but that's a separate indoor elephant).

My question:

Is it OK to change a longstanding function to treat None like an absent parameter, where previously it was an error? (This also entails a docs update and maybe a changelog entry)