1) A rule must be applied that prevents users from gaining exp by commenting on articles that are in full voting, they can only earn exp from those comments until the article is approved by the moderators.
2) There are users who only care to send spam comments on old articles to be able to level up, so it is recommended that articles that are more than one year (maybe months) on the page no longer receive future comments as a way of automated blocking, although to some extent moderators may be given the right to lock (and reopen) articles as a totally manual measure.