plus could have a mini privacy service to stop swearing on IM

I doubt that'd be included in Plus, due to the number of different ways in which you can swear in various languages.
However, you can set up some Word Filters to at least censor swear words in your own language

you can set up word filters with Messenger Plus!, where the words you recieve and/or the words you send are filtered to be sent/recieved as different words

e.g. you san set the word "Dog" to be changed to "Cat" when you recieve it. Or you can set it to where the word "Dog" is changed to "Cat" when you send it to your friend, therefore making him only see the words you set to be sent.

Thxs