"You know more about this than me/I" [duplicate]

My guess is both are correct. The first than is used as a preposition while the second one is used as a conjunction.

Note however, to me, the first sentence means you know more about this than you know about me while the second one means you know more about this than I know about this.

The first uses than as a preposition having me as its complement. The second uses than as a conjunction to introduce the elliptical clause I (do). ‘The Cambridge Guide to English Usage’ reports that:

Research associated with the Longman Grammar (1999) showed that speakers mostly use than (and as) as prepositions (i.e. with a following object pronoun) and only rarely with a following subject pronoun. Fiction writers make about equal use of the two constructions, while academic writers use neither.

No one need hesitate to say You know more about this than me.

The second sentence is, indeed, the correct one. If in doubt, always try to fill in the missing words - just as you did.

You know more about this than I do/know.

If you don't, your sentences might get misinterpreted. Consider this example

Sara likes cake more than (she likes) me.

or

Sara likes cake more than I (like cake).