Hi again
well last year i was testing partition prune and i checked that a insert isn´t pruned since i executed a partition alter table on a partition X and inserted a row at partition Y, and the result was a insert lock until alter table end...
the bug/feature request was reported at mysql team, but i don´t know why they don´t accept more feature requests just bugs (maybe a oracle principle of only enterprise clients)

check:
http://bugs.mysql.com/bug.php?id=60190

could be nice to have a lock per partition and not per table, there´s a problem since .frm file is a file to all partitions and a lock of a partition may lock this file, and this get back to a lock of table and not a partition lock

well i think at bug sent to mysql is better explained
thanks