It's generally harmless if people send corrupted packets, but having the error appear in "errors" makes it look much more serious:

"errors" : "EXCEPTION: NSt8ios_base7failureE       \nnon-canonical ReadCompactSize()       \nbitcoin in ProcessMessages()       \n"

This happens due to the use of PrintExceptionContinue in the catch clauses, which set strMiscWarning.