Is it a bug, though?
I just merited you with:
1-.
Seems like it just ignores everything that isn't a number, which feels like the ideal behavior.
If I ever see a super B post I'll try something like "1-.0" to see if it sends 10 merits.

Then I tried the opposite
-1
And it says invalid. This means "-" placed at the left side makes a number but at the right side is just a sign.