sober - worthwhile discussions

If one has not followed a discussion from the beginning (e.g. at a mailing list), often it is necessary to read a lot of (scattered) text to understand the state of the play. Many people do not have the resources for this and thus

1. abstain from taking part in the discussion or
2. take part without knowing what has already been discussed.

Both consequences are unwanted if the discussion is intended to have consequence which the whole group can accept.