well, if whatever code automatically turns plaintext links into hyperlinks isn’t Markdown related, then it’s still the instance or client you’re using that has the problem. before they edited the trailing space in, it was working correctly on my end. You should consider looking into it and filing a bug.
If I were to speculate, I’d say it came from the == operator (Boolean equality comparison) and then later, when that was extended to include Boolean less-than-or-equal and greater-than-or-equal, the decision was made to keep them 2 characters long. Either because it was visually cleaner, or just because programmers love being lazy (read: efficient)