hacker45:

hmm i guess that's reasonable but how can he catch one out of a million conversation spammers?

Nobody sifts through conversations looking for your personal secrets, people who abuse the Conversations feature (spam, insults, etc) are caught when they are reported.

As for the initial question, I don't allow editing of conversations simply because of the potential abuse, with an edited forum post, there are hundreds to witness or report it, if I send someone a conversations telling them to 'Go **** themselves' and later remove it, It's their word against mine since evidence has been obscured.

Another reason is that editing forum posts is allowed is to prevent double posting, since double posting is not an issue in conversations, you may simply post your corrections as an extra reply.