Erik Darling opposes expansive numeral policies:
A while back I blogged about how ISNUMERIC can give you some wacky results.
Working with a client… Well, it’s hard to know based on my publishing schedule. But they were using ISNUMERIC all over the place, and getting the same wacky results, and even errors.
Click through to see what types of things ISNUMERIC() considers to be numbers and for a couple of alternatives.