Title is quite self-explanatory. Consider the variable edit_delta, and take 2 edits, one with edit_delta > 0 and one with edit_delta < 0. On the first one, if you do edit_delta === ## will return true, while on the second one it won't. By examining vars from JS console, however, a negative edit_delta appears as a number, as expected. This isn't that big problem, since usually edit_delta is used in a comparison (< or >) where the value is casted to number and works fine, but we'd better fix it anyway.
ADD: Oh, the funny part! edit_delta === '-##' returns false as well.