Semantics Question: epigenetic mark on a person's DNA?
We may restrict your definition of epigenetics as heritable changes in an organism's phenotype that occur without a change in the sequence of DNA bases. That is, changes to the DNA molecule itself is permitted, as long as the sequence of ATCGs are not affected.

In this sense, it would not be wrong to refer to an "epigenetic mark on a person's DNA". For example, a mechanism of epigenetics that does directly change the DNA molecule would be something like DNA methylation.