Similar replacements in language entries are wrapped by different kinds of quotation marks, for example here language/en/common.php

	'NOTIFICATION_POST'					=> '%1$s replied to the topic "%2$s".',

	'NOTIFICATION_POST_TRIMMED'			=> '%1$s and %3$d others replied to the topic “%2$s”',

we can see

"%2$s"

rounded by U+0022 quotation marks and

“%2$s”

rounded by U+301D/U+301E ones (as far as I can see it).
Although I'm not sure if it's a bug really.