To be clear, I didn’t start this thread. Apparently other people are allowed to start threads under another user’s name (so called “splitting”?). It would be nice if the person who appears to be the OP in a given thread was contacted prior to creating such a thread.
Anyway… I suppose one useful aspect of encrypted transmission of “public” email would be anonymity. While PGP encrypted personal email affords users more privacy, public email postings aren’t just an archive of postings. They also entail the transmission of content.
My understanding is that email passes through many points in a network on its way to a recipient. Email content can easily be snooped along the way if it isn’t encrypted, which might perhaps make it easier to correlate public content of an email with certain IP addresses, potentially exposing the source of that email.
So even if someone has a random username and/or email address displayed on public postings, their anonymity could potentially be threatened during the transmission of those postings - a kind of breadcrumb trail leading back to certain IPs (or at least narrowing down the pool of candidates).
I think the real question is why isn’t email encrypted by default? HTTPS is now extremely common place and the benefits of encrypting network traffic for websites is well known. What exactly are the benefits of not encrypting email? Convenience? I suppose TLS isn’t convenient either, but once it’s set up, it’s a non-issue. Once email is set up to encrypt between two parties who have each other’s public keys, it’s trivial.