Hi there,
If you edit your Post and Thread events, you'll notice there's a "Negation Amount" setting (exact naming might be slightly off, but it'll have the word Negation in it). This is what's used for if a post or thread is edited and then saved, or if a post or thread is deleted.
For instance, if you grant 5 points for a new thread and 1 for a new post, if someone edits their post, first the "negation" amount is applied, then the amount is re-applied.
The reason for this is the fact that you have an option to award people a variable amount of points depending on the post length. Therefore, the old amount needs to be removed before the new amount can be re-added.
In short; if you set the Negation amount to the same amount as your "normal" amount, this won't be an issue.