How does one request deletion?
Discussion
On amethyst the option is on the three dot menu visible from the note.
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