This. I've had my email for years. Admittedly my engagement on HN is chaotic and somewhat rare but in all those years, I think I've had half a dozen one-off emails.

Maybe that shows the actual benefit (or lack thereof) DM would have?

I mean "one-off" suggests that what you received might not have delivered significant value -- what I get is usually please-use-my-product marketing encouraged only by my non-negative commenting.