- Nonstandard spelling of more so.
Though frequent in informal writing, some arbiters of English usage consider “moreso” an incorrect form of “more so”, sometimes citing the fact that in many cases the "so" is included tautologically, and the word “more” is all that is needed. "Moreso" appearing in print may be a typo in the form of an accidentally omitted space.
However, if used correctly, the "so" part stands in for "thus" or "the case" (as "so" has more than one meaning) for example: "It's moreso that 'moreso' just isn't used correctly, rather than it being a tautological monstrosity." In arbiter-friendly English, this would be: "It's more the case that 'moreso' just isn't used correctly..." Also, it seems logical that a statement containing 'moreso' should follow on from a clause or sentence expressing a comparison to what will be dictated as 'more' in the following clause or sentence.