The auto archive feature archives discussions which have no posts for the
selected time (e.g. 3 months). However, currently it also includes sticky
discussions. Sticky discussions are supposed to stay on top even when there are
no new posts, so it is inappropriate to archive these discussions.

Unfortunately I didn't think of this when specifying the feature; a course team
has just noticed it.

Could we change the feature so that sticky discussions are never archived.