The original comment was "drop the index for being "too complicated"". Having to go from "working tree -> index -> committed". In comparison Mercurial only has working "tree -> committed" and Jujutsu only has "committed". The idea of dropping the index is to avoid having extra states changes must pass through. Technically Jujutsu still has the index, as it uses libgit, but the concept isn't exposed to the end user.
>this will just lead to more devs not caring about properly splitting up changes
I strongly disagree. jj split reduces the friction in splitting commits. Just think what you have to do to split a commit with git following your 2 step guidance. git reset HEAD~ && git add -p commit && git add -A && git commit. It's even worse for jj split -r @-- (split the 2nd to last commit (ignoring your working commit)). For git you have to do git rebase -i HEAD~2 && git add -p commit && git add -A && git commit && git rebase --continue. In the interactive rebase ui you select the 2nd to last commit to be edited. People avoid splitting with git because there is too much friction. It takes too many commands. It's hard to remember. You can screw up and waste even more time. If you want to encourage devs to split up commits then make it easy to do.