When viewing your flag summary, you are presented with a list of flags, sorted by post. If you flag a bunch of comments on the same post, those are all listed together... including pending flags on those posts. Those pending flags raised later than the handled flags, will then show under the handled flags on that post:
...or, for a slightly more extreme example:
When scrolling through the flag summary page, it'd be more useful to see which ones are pending on top of the handled ones. When they're buried under the handled ones, it's easier to miss.
