prepending "zzz_deleted_" might exceed the maximal lenght for column names
I found that renaming a column to "zzz_deleted_tx_powermail_tellAFriendForm_receiverEmailContentField" didn't work because if it's size of 66 characters. MySQL allows only 64 - therefore I suggest to add that limitation also to t3lib_install_sql.
At the same time the patch has to make sure that the shortened names don't create collisions - therefore the field names are cut of from the beginning of the name because it's less likely to create collision this way.
See MySQL documentation: http://dev.mysql.com/doc/refman/5.5/en/identifiers.html