The tag team of Mark Jaquith and King of Fools have, apparently at least, fixed the bug that has been causing machine language characters to appear in blog comments that included pasted quotation marks, em dashes, and so forth. Let me know if you have further problems.
UPDATE: Unfortunately, fixing the bug apparently created a new one: Now, typing quotation marks in a comment will cause the comment to truncate immediately before the quotation mark. I’ll update when that’s fixed.
UPDATE: Fixed. Let me know if there are other issues.
