Recently, I was looking at Dungeon Defender questions when I noticed a slight inaccuracy in one of the answers. The ETA of a patch. It was originally the 7th, but had been changed to the 9th. Unfortunately, a simple change from "7th" to "9th" wasn't allowable. I had to edit more!
I ended up just using the long form of the date to get around it, but such a system seems unnecessary and arbitrary when you have to have a high amount of karma to make edits without approval.
This is a deliberate limitation across all sites, to avoid trivial edits. In your case the limitation is definitely annoying, since that 1-character edit is decidedly not trivial. You can raise this issue on SE meta, but in general, the accepted work-around is to just add a few more actually-trivial edits into your edit. Fix spaces, punctuation, whatever little things you can find.
If you can't find anything, you can always add "invisible" information, such as an XML comment: the text <!-- edited for character count --> will not be seen.
Also note that the Edit Questions and Answers privilege, unlocked at 2,000 reputation, removes the character edit limitation.
I don't think that there's a need to change a network-wide policy for something that can easily be handled through existing tools, and I would prefer not to encourage people to find ways to get around the limits without improving content. It's simple enough to leave a note for the OP to update the answer and then to flag your comment as obsolete once the change has been made. If that isn't the situation you prefer, then consider it as motivation to earn enough rep where you can make those edits yourself!
There certainly are instances where a single character completely changes an answer, but changing the policy to permit those answers also permits the trivial edits that it was designed to prevent in the first place. Lowering the bar means swamping reviewers with low-quality changes as well as the few important edits that this change would permit.
