I think it is okay to accept liberally as long as you combine it with warnings for a while to give offenders a chance to fix it.
Through the appropriate channels; in-band and out-of-band.
It also does not give any way to actually see a warning message, where would we even put it? I know for a fact that if my glibc DNS resolver started spitting out errors into /var/log/god_knows_what I would take days to find it, at best the resolver could return some kind of errno with perror giving us a message like "The DNS response has not been correctly formatted", and then hope that the message is caught and forwarded through whatever is wrapping the C library, hopefully into our stderr. And there's so many ways even that could fail.
Start with milliseconds, move on to seconds and so on as the unwanted behavior continues.
A weak warning that's just an entry in a scrolling console means nothing to end users and can be ignored by devs. A strong warning that comes out as a modal dialog can still be ignored by devs and then just annoys users. See the early era of Windows UAC for possibly the most widespread example of a strong warning added after the fact.