Pasting one of those characters in, we see it's counted as one character. However: Twitter replaces all URLs, even shortened ones, with 22-character t.co URLs. Using 9m.no on Twitter is pointless, especially since Twitter displays the original URL for t.co URLs only. Using another shortener, the shortened URL is all that is shown, which isn't very reader-friendly.
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Pasting one of those characters in, we see it's counted as one character. However: Twitter replaces all URLs, even shortened ones, with 22-character t.co URLs. Using 9m.no on Twitter is pointless, especially since Twitter displays the original URL for t.co URLs only. Using another shortener, the shortened URL is all that is shown, which isn't very reader-friendly.