I would say that the real performance drain is top posting, which seems to go hand in hand with HTML emails.
With top posting, in order to read a mail - especially one that is a few levels deep in a thread - becomes an exercise in jumping back and forth, trying to find context and make sense of who replies to what, finding relevant sentences (often hidden in a mess of signatures).
With bottom posting and proper curated quoting, context is a glance away, and it's easy to see who said what in reply to what.
I'm sure this would be possible with HTML mails as well, but I've never seen it happen. It's all just a mess of hard to find information in the least sensible order imaginable.
It is not, so long as you first quote the relevant part you are replying to.
At some point you can also trim the tail as you see fit (I don't find it necessary because my mail client does a good enogh job at hiding that part unless I click on a "show wverything" button.
Technically it appears that I'm advocating for a combination of inline and top posting. Quoting the relevant wikipedia part:
> The interleaved reply style can also be combined with top-posting: selected points are quoted and replied to, as above, and then a full copy of the original message is appended.
Indeed, it would be nice if the netizens of the world would wake up to this. Sadly, I think it's unlikely to improve any time soon and so I'll stick to top posting and threading in the email client.
With top posting, in order to read a mail - especially one that is a few levels deep in a thread - becomes an exercise in jumping back and forth, trying to find context and make sense of who replies to what, finding relevant sentences (often hidden in a mess of signatures).
With bottom posting and proper curated quoting, context is a glance away, and it's easy to see who said what in reply to what.
I'm sure this would be possible with HTML mails as well, but I've never seen it happen. It's all just a mess of hard to find information in the least sensible order imaginable.