There are different types of epigenetic mechanisms anyway which have different levels of persistence/reprogrammability, so to dive into technical details one wo

There are different types of epigenetic mechanisms anyway which have different levels of persistence/reprogrammability, so to dive into technical details one would need to get very specific. Different methods for changing the DNA sequence would also have functional differences in how they could store a memory. And it's important to distinguish these mechanisms on a single cell level versus how they function in the body as a whole. In a single cell I wouldn't call VDJ recombination memory, it's just an efficient way of encoding many different possibilities for types of receptors (and then selecting one). There exist many cells in your body that match a potential antigen you've never seen before - it's just that there are an extremely small number of them. The memory is really encoded by increasing the population of that cell in the body. Which has different storage properties than the individual cell's DNA does. Epigenetic change to a single neuron is unlikely to have a functional effect either, but it is a change that can occur to a mature cell as a reaction to the environment, in a way that VDJ recombination is not. AFAIK there is a lot left to be understood about how epigenetic modifications affect the brain. I agree this is all interesting and can have implications for computational models, but there are models at many levels of abstraction. So I don't think it is necessary to get at the biological details in order to discuss higher level computational implications. Questions about the capabilities of the memory for each individual neuron would arise, but they could be theorized about without much knowledge of biological details. Of course it depends what your goals are whether you would consider that useful. Anyway, I think we're both in agreement the OG comment was wrong, I just feel that "in DNA" is very ambiguous, and also not really the problem with his comment given the purpose of HN.