Formatting note: The bookmarklet italicizes the comment snippit and includes the username and a link to the original comment. The username and link are omitted for short threads (and in cases where authorship is unclear to the script).
1. Install the quoting bookmarklet.
2. Navigate to a metafilter.com thread.
3. Highlight comment snippit.
4. Click bookmarklet.
Note: Safari and Firefox only.
The bookmarklet should now work on Metafilter, Ask Metafilter, and Metatalk