There you could type on the prompt line and then call jinx or your quote wrapping function etc as it's just a normal Emacs buffer. You can't edit the scrollback buffer though, but I don't think that's possible in eshell either.

But line-mode has it's own set of problems. Since we don't send anything to the shell, you could have some problems with autocomplete or similar things that change the text depending on each typed char. Similarly we automatically disable line-mode when you enter a TUI (alt-screen) app, as line-mode doesn't make too much sense in e.g. vim. But that's configurable and you can still force line-mode, it really depends on the TUI apps.

We try to support as much as possible and work around things like fish autocomplete etc. But please try and report any issues you find.