On amethyst the option is on the three dot menu visible from the note.
Discussion
Interesting, Damus doesn’t seem to have that yet 
I'm not sure how effective it is with older notes, but twice I have been able to withdraw notes immediately after posting them when I saw a glaring mistake.
Everything online is practically permanent so I'm developing a more consistent proof reading practice 🙂
"replace" is function is the way here.
replace your note by a black hole img like this
addendum: some say they can see black holes