When I first read about DNA methylation for memory storage in the nervous system, I also found it silly… because we are so used to the classic principle of synaptic learning.
But this Nature article seems reliable and the author’s deep background in hippocampus & synaptic plasticity makes it even more serious:
https://scholar.google.co.uk/scholar?as_q=&num=10&btnG=Search+Scholar&as_epq=&as_oq=&as_eq=&as_occt=any&as_sauthors=“Wickliffe%20C.+Abraham”&as_publication=&as_ylo=&as_yhi=&as_allsubj=all&hl=en
So, I think it is worth paying attention to this provocative idea, who knows…