For consistency, the changes made in 30495ea1f904953784fb36751d55da233d616215 (T157418) and b3dd3881b2fae3c966f0c9204a3c5ac982fa1f64 (T25393, T47803) should handle (ignore) unicode whitespace by using (\t|\p{Zs}), not just [ \t] (or \s, which includes newlines and has other weird stuff).

That's consistent with the way magic links and external links are parsed.