<Like you say, editing would allow posters to sneak around their own statements, unless there was some way to show what was edited (very complicated.)

Yes...but would keeping a history of previous versions of a message, available to anyone, serve to hold people accountable for their words?

Wouldn't you expect that the knowledge that a person could be called on attempts to weasel out of responsibility for what he/she wrote would be a powerful incentive to stick to the straight and narrow?

Posting clarification messages usually works against clarification, to me, because you have to integrate the changes in the clarified post with the original. Much the same hassle as having to compile a ton of engineering changes notices to an original spec to find out what it really says. Seems to me that it's the author's responsibility to tell a coherent story, not mine to sort it out and piece it together.

--Robert