I have always edited my posts (usually within a reasonable amount of time, depending on how fast it takes for people to respond) since when I realized that forum posting often mimic several people posting, essentially, mini-essays.
I myself, being an aspiring writer before "living" on the internet, tend to see this as a good thing actually: it provides a snapshot of previous stated opinions, arguments, etc., but allows you to either mark you original post with an "edit:" timestamp, where you put in the additional remark to clarify your OP, or continue the conversation with a newer post.
Usually, I do the later if a thread is hot (busy); I tend to do the earlier if a thread is either "cold" or "dead". Of course, sometimes I forget about threads entirley; there is the whole "offline" world that can get in the way of internet activities.
With the advent of Googling one's own internet alias', I find it amusing & sometimes informative, to go back and see what I've written. I actually went back and did this with a few previous comments (in general, on the web) to help in an essay I was constructing. I do not see this as perfectionist or obsessive-compulsive; but then again, when it comes to such diagnosis, I am naturally skeptical of labelling people (or myself) as such, especially when the said possible diagnosis is made on a person who isn't negativley affected by it.
This also explains my extreme oppositon to the intellecutally pathetic attempts at marginalizing people who "use the Internet too much", by concocting an Internet Addiction Disorder (IAD). That is another argument entirley, but I will say that it's absurd in it's vauge, general definition (MMORPG's, on the other hand...).
I see it as a naturally occuring behavior in response to the capabilities of forums, blogs, and even IM Away message's; or in general, a response to technology.
I'd bet rates of insomnia stready increased with the advent of the light bulb, lol.