Hard-wrapping paragraphs to a desired length in the original log allows humans to decide which lines should wrap and which ones shouldn't, without a pile of complexity similar to HTML, Markdown, or some other markup language.
soft-wrap:
- to allow the presentation layer to soft-wrap a line, just don't add a newline.
- for new paragraphs, just add two newlines as usual
- for indent sensitive code, diagrams, etc. add newlines where appropriate, taking care to not exceed 74 columns for any line. Everyone does this already.
+ tweak:
- in the presentation layer, soft-wrap all lines except those less than 74 characters long.
This isn't perfect for terminals less than 80 characters wide, in that the diagrams won't fit, but nobody uses narrow terminals, and Linus' scheme is even more broken for this case, so it's strictly better. It also allows one to easily distinguish diagrams from non diagrams by eyeballing the text flow. Best of all, it makes fewer assumptions about terminal width.
And what's stopping someone implementing this?
Most likely, not wanting to inflict such a syntax on git users, when the current approach works just fine.
But nothing stops someone from writing a patch with an off-by-default option for such a syntax, and proposing it for inclusion.