How difficult would it be to detect cross-posts when the relevant questions have identical titles and content, and are posted by the same user? As an example:
- Original, posted on SO
- Following day, migrated to SO from SF
- Also following day, migrated to SO from SU
If this is technically possible, I'm not sure what the best response would be?
- Notify the user when asking the question that cross-posting is not allowed.
- For off-topic cross-posts (e.g. the above example): Let the question be closed as off-topic, and then automatically block or flag the question as an exact duplicate during migration.
- For on-topic cross posts (eg a game programming question on SO and gamedev): Not sure what the process is for flagging/closing cross-posts, but whatever it is, can we automate some aspect of that?
- Something else?
(Edited to remove request for auto-detecting same-site re-posting, which has already been implemented since the example I listed occurred)