Should a marker TA handle students' marking issues by email? I am a university marker TA. The instructor requires TAs to meet students if they have marking issues. But I found most students just come to meet me for better grades, not to ask questions, and some are tough to handle; they just insist they should get better grades.

I feel that is annoying. Is it a better idea to handle the cases by email, and let them talk to the instructor if they have further questions?
Part of the rite of passage of being a graduate student is having to deal with insistent students in person.

If students ask for more marks, you can firmly but politely state that marks are not subject to negotiation, but that you'll gladly discuss the contents of the answer.

Aside: learn early to be firm for otherwise word will spread you are soft and you will invite more headaches.  Being firm can lead to awkward silences as you may rapidly reach a point when there is nothing more to say.  If you reach a dead end you can always close by firmly but politely ask if there are other topics to discuss.