Listing posts by a specific user with a specific tag fails for some older posts, probably because they've been retrospectively tagged.
posted by Burger-Eating Invasion Monkey to Bugs at 5:10 PM (5 comments total)
For instance, look at two posts about juggling
recent one by staggernation comes up in a search
for staggernation's posts about juggling. This
one by MiguelCardoso doesn't come up in a search
for MiguelCardoso's posts about juggling — I'm guessing that it's been retrospectively tagged, and that retrospective tags don't work with the user-searching feature.