mhack – Macros for marginal notes, in Plain TeX

Th­ese macros present two macros for in­sert­ing marginal notes.
The first (\ihack) uses an in­sert to build a mar­gin-full of notes, start­ing at the top of the page; the macro re­quires changes to the out­put rou­tine.
The other macro (\vhack) just \vad­justs each note to the hor­i­zon­tal po­si­tion where it starts; this re­quires no change to the out­put rou­tine, but pro­vides no pro­tec­tion against notes col­lid­ing with each other.