it's forumese. being mantled relates to posting something and then being totally ignored by subsequent posts, often saying much the same thing, as though you were cloaked in a shroud of invisibility. and yes, this is sometimes even further obfuscated and referred to as being Mickey'd.

the other is responding to a post with a really apt and/or witty reply only to discover that (often whilst you were actually composing) someone else pipped you by posting much the same reply -- yes, pipped at the post; exactly!

-joe (I expect by now I may have been pipped on this reply) friday