When moderators decline flags, they have several predefined reasons to choose from, as well as the ability to type in a custom message.
There are several phrases I still find myself typing in repeatedly to the "other..." field, so I consulted with other moderators to see if we could come up with some additional suggestions for common messages to be added to the dialog above.
Will not delete. Other people may find the answer(s) useful.
This one is to be used when users flag their own open and answered question for deletion. People often do this when they want to remove an old question that they're embarrassed by, or when they posted code from their work or school that they shouldn't have. If the question is already closed or has received no answers yet we can just delete it, but if they've received useful answers these types of flags should be declined.
Questions older than 60 days cannot be migrated. See Disable migration for questions older than 60 days.
People often request migration of older closed questions to new sites. Right now we still have to decline these fairly often, but hopefully that will change as more people learn of the 60 day limit. (Meaning this option could possibly/hopefully be retired at some point in the future.)
This post is extremely bad and/or off-topic but it is neither spam nor offensive. Please do not use those flag types for simply bad posts.
People often abuse the spam/offensive flags to get moderator's attention for posts that really don't require immediate action (or any action at all in some cases). This seems like it's on the rise lately on Stack Overflow, so we decline these flags to try and discourage people from abusing them.
Any suggestions for improving the clarity of these messages would be welcome.