[tolciho]

Such as the base OpenBSD vi, which only supports a single-level undo, which I am using at this moment (and still learning how to use, after a few decades). vim got curb-canned a while ago due to various "that's nice, but how do I turn it off?" additions, in addition to having more code in header files than vi has in total. vi meanwhile is pretty bloated though has ex filters which are a huge step up from the standard editor. Multi-level undo? Don't really need it.

[somat]

For what it's worth obsd vi (nvi) has multi level undo. it is just the slightly awkward 'u' to undo/redo then '.' to repeat the undo/redo.

[Sharlin]

But hey, at least it’s POSIX compliant! In that respect, anyway.