John (Hardly), The thread question is dead as far as I'm concerned but I've just another read and was wondering where you got this from:

I was once told that an edited post is a MUCH bigger file than would seem proportionate to the size of the post.

I suspect you are confusing it with editing a post using an external editor such as MS Word to produce HTML (as opposed to just straight copy/ paste your text from one to another) to use in a post or for a web page for that matter.

The amount of junk created in that process can be quite horrendous.