After the last monster recalc took me below 20k I should still have had the 10k ability to delete things.
I went to this post to cast a delete vote, and found that even though I'm still over 10k the
delete link didn't appear. Note that in the
delete tab of the 10k tools it shows as having two delete votes (as of the occurrence, as per this pic).
EDIT: As Grace Note pointed out, in February (2011) they changed it so 20ks could delete posts immediately instead of waiting for 2 days.