Well, the good thing to seeing when someone has changed something is that you see it. With this being a discussion board and opposing viewpoints being the norm, having someone say something then change it later can make a debate or discussion impossible to follow if you don't know the person isn't being consistent. It was never meant to track how many times you have spelling or grammar changes so if you're worried about that, don't be, just do whatever works and stick to your message if you have to edit it later.
Another possible thing you can do it this...
edit: I'm just putting this example of an edit, here's what I did - typed an example. You can be straightforward with what you changed in notes after the message.