A sardonic person is a person who is scornful and mocking to someone in a humorous way.
If someone is mocking you in a humorous way and not meaning any actual harm by the humorous mocking they are doing to you then that person would be a sardonic person.
However even when someone is mocking you in a good way it still can be hurtful to you.
So if someone is mocking you in a good way but it's hurting your feelings or you do not like them mocking you that way then you can tell them in a nice way that they should not mock you.
Now if someone is just mocking you to actually hurt your feelings then that person would just be a bully and not a sardonic person.
Some people call people bad names and mock them in bad ways and actually do mean harm.
I have a friend that is overweight and we both joke about her weight but not to make fun of her.
She finds humor in the weight she is and we both bust out laughing at some jokes that she even makes up about herself.
She's a very humorous person and very happy even being overweight and she doesn't care if someone actually does make fun of her weight as she jokes right along and the bully doesn't get what they want and move on to someone else.