> - It is rare that the problem is the limiting factor. In Emacs, which has horrible problems rendering long lines, usually by the time I realise there is a visualisation problem my editor has died.

Sounds like the problem is your editor, not the Clojure namespace :)

Maybe try a real editor, such as vim/neovim ;) It gets a bit bogged down, even on my desktop computer, but at least it never crashes.