If we look at these two sentences:
A. This is more serious than what people think.
B. This is more serious than people think.
Is using "what" there grammatically incorrect? Or are they the same? Is one more idiomatic than the other? When would you omit "what"?
Thanks!
In this case, go with option B. The unelided sentence is "This is more serious than people think [it is]."
By adding "what", you're introducing a relative clause, which is supposed to add more information. But you don't need further clarification, you need just a simple comparison.
Option A isn't "grammatically" incorrect, but it doesn't mean the same thing as B. Instead, the comparison isn't on how serious people think something is, but on what their thoughts are. Written out logically, option A means that this is a more serious thing than whatever it is that people are thinking. It's their thoughts that are less serious, not that they underestimate the seriousness of whatever this is.
