hey, I just discovered what to do when this problem happens. If I come onto afterlife conversation from another computer, or even if it's my own other computer?
I often enough would encounter there would no longer be a modify button or delete button to change the mistakes in my post with.
although I would be logged in automatically, so I couldn't figure this out and started dilly dallying around with system preferences, when all you have to do is "update your session."

it's a little session update button on the top under the date where it says other buttons like Home, help, search, etc.  it says Session or Session update.

lol. do u ever click on somthing and disaster awaits? I do. but this time it worked. then your computer should ask for your password. and all the modify buttons are then restored.