The message wall desperately requires some usability enhancements.
1) The limit of 500 characters is fine, however there needs to be a character counter OR don't delete the message, just allow it to be edited to reduce the characters to the required 500 or less
2) The inappropriate word filter functionality needs drastic improvement. I lose at least 10 messages a day using no more than Grade 6 standard English (with English spelling, NOT American spelling - could that be an issue?). Again, the message is deleted. Given I have NOT used any inappropriate words (unless "undroop" is inappropriate in some manner I am unaware of), I have no idea what word not to include when I retype. Again, leave the message intact for the user to edit, highlighting the offending word.
Just now I have had both happen one after the other. I've told my neighbour I give up and will return to answer messages later.