"The long answer is that plywood is an acceptable substrate for
Only exterior grade, or CDX plywood is acceptable for
Since the poster is removing vinyl from 1/4" plywood, it's
probably smooth, thin plywood that is traditionally used
under vinyl, and is the wrong type to receive tile.
Other backerboards would be a better choice in a kitchen
As has been said, you need 1 1/4" of solidly glued
and screwed subfloor if you want a long lasting job.
I've seen many DIY'ers tile over that thin smooth plywood
and it doesn't last. Generally too it's not bonded very
well over the subfloor, as it doesn't need to be for vinyl.