I never seek to add columns where an attribute does not exist in the reality being modeled; sometimes I do end up adding something 'artificial' but only when there is a "good data modeling" reason for doing so.

May I add to that? When you design -- yes, actually design and not
blindly throw on the first thing at hand -- an artificial key, you
also have to create and document the validation and verification rules
for it.

I am a fan of check digits if this data element has to come in thru
application code front ends. When we get SIMILAR TO in more SQL
products, I will do more with regular expressions.