Change default method to retain unwanted posts instead of discarding them (if supported)

Goal

• Decrease the impact of inappropriate content classifications by retaining unwanted posts instead of discarding them - if supported.

Details

• Very rarely (as in: 1 in ~10,000+), a post may be inappropriately classified and blocked as spam.
• If that happens, most users don't really recognize that those other ~9,999+ posts were successfully and appropriately classified as ham or spam.
• Discarded posts cannot be restored, so any false-positive cannot be corrected.
• However, some protected forms allow to retain unwanted posts (as unpublished) instead of discarding them.

Change proposal

1. Make "Retain" the default option value for forms that support it.

   (i.e., just the default, can still be changed to "Discard")

2. Iterate from there.

   (e.g., figure out ways to only retain posts that are worth to retain, implement a better basic moderation queue, etc)

Notes

• This change proposal is likely heading into the same direction as ongoing/future demands for Mollom Moderation integration will.