Joe, I know I am a couple of days late but with regards to deletions, I think I would draw the line with:

(1) Anything libellous and slanderous.
(2) Posts that are offensive towards sections of society -ie racist, sexist, homophobic, etc. generalisations.
(3) Gratuitous use of foul language.
(4) Personalised offensive language directed at people on the basis of their gender, race, sexual orientation, disabillity, age, etc.