webchick talking to Michelle in IRC #drupal:
I name all my patches as {module_name}-{description-of-changes}-{issue_node_id}-{issue_comment_id}.patch
Personally, I think issue_comment_id might be hard to do (even interpreted as the big #5 etc project module places in the comment title, rather than the internal Drupal ID!) since people can add comments while you are making the patch, but I'm on board with the ideal.
Getting into that habit also really forces you to keep to a one-issue-one-change thing.