This has been bugging me for several years, but it took a Miss Manners column to make a post about it.
I sometimes find Miss Manners’s answers to be crotchety and a bit mean, but this was right on.
Why add the preposition? The word is already complete. Merriam-Webster says that in this context welcome is an interjection that is “used to express a greeting to a guest or newcomer upon arrival.”
See? One word. Done!
And “in” to what? If one is trying to say “Welcome to my store,” or “Welcome to the store,” the word “in” is not used. Do they mean “inside” like “inside the building,” or “inside the door”?
I’m certainly not engaging with people who say this and badgering them as to if they are even thinking what they are saying. It is one of those things I could let go of, but so far, it continues to rankle.
I’m hoping it goes the way the overuse of air quotes did in the 90s.
Come to think of it, air quotes would be perfect for this: “Welcome [air quotes] in [close air quotes]”.