>This text box I'm replying to you with is a plain text textbox. It word-wraps just fine.

No it doesn't. In fact I had to edit a comment I made above this one about four times until I got the formatting right. It annoyingly ignored me doing this:

    line one
    line two
    line three

and assumed I meant this:

    line one line two line three

You're talking about the comment output, which is html after being processed. The text box is plaintext, and it word-wraps :)

The text box and the text output are the same thing: markdown. A little tickbox that just wrapped every message I send in a <pre> tag would be lovely.

You're missing my point because you don't understand the meaning I'm going for here. The comment box is not markdown, it's plaintext. This is not a rich text WYSIWYG editor.

My original point is that plenty of software does plaintext wrapping just fine and it's pretty ridiculous that consoles are stuck in this 80 character mindset.

No you're missing the point. A computer cannot wrap text reliably. It does not know how to.