" Well, actually, I use <ecode>, because <code> appears not to honor line breaks and <ecode> appears not to honor indentation, and, for code, the latter sucks less than the former."
Exactly the sort of Hobsons choice that you should NOT have to face, frankly. Text is text. It's absurd that 'designers' have so much trouble dealing with it.
Now that aside, notice you are talking about explicitly tagging your text, which I am not doing. I am only using the posting mode default setting, I rarely insert tags and when I do I switch posting modes.
"Neither of them appear to provide me with any advantages if I'm just posting text."
They are far from perfect but they do indeed suck a little less. I used to use the 'plain text' as my default but there are several cases where that mode will strip and/or add tags in a pseudo-random fashion and it pissed me off one time too many.
If I type in https://google.com/ I dont necessarily want that to converted into a link, for instance. Relatively minor.
If I type:
x 4 5
y 3 2
z 1 8
Then I MUST use code or slashdot will simply destroy the entire paragraph. The amount of time I had to spend to make that short snippet of *text* display properly just now is significant and absurd. But if I were posting in any mode other than 'code' it would not have been an absurdly difficulty task to accomplish a simple and obvious result, it would have actually been IMPOSSIBLE.
ALSO I cannot even mention a tag (<tt> for example but there are many others) without switching to code. If I try to say "<tt> sucks" for instance I must do this with 'code' set - otherwise the tag does not appear, it is parsed and changes font for the rest of the post! Absurd.
Again, there should be no problem reading the text. If there is a problem reading the text, then local browser settings need to be corrected. While what slashdot is doing here is certainly not what I would call sane or recommend, it is in fact workable and that one stalker I have attracted is rather more insane for refusing to choose a readable <tt> font.