These conventions seem to be a de facto standard in plain text, especially email and (most Usenet) newsgroups: Some would argue this is no longer relevant in today's world of word processing, HTML mail readers (and the ever-popular HTML newsreaders). I don't agree, for a multitude of reasons.

First, email and news are not hypertext, no matter how hard you try to make them. Plain text email and news are alive and well, not to mention standardised. (There was an effort to standardise this sort of "rich text" several years back, but there didn't seem much call or need for an RFC). Gnus can display all these conventions when they appear in plain text.

Second, even if you don't like them in communications, they're still worth using in other places which mandate plain text. It's nice to be able to add emphasis in your comments.

Finally, they're very easy to read in text!