Fixed in the next release. This occurred because of a major difference in moderation checkbox position between vBulletin (right of post) and XenForo (left of post), where the Javascript was expecting only a right-of-post positioning (even though vBulletin doesn't even use overlays!). This is fixed by determining whether there is more room on the left or right side of the checkbox before picking a side the place the overlay on. If there is not enough room on either side, the overlay will be placed on the next line. This is consistent with XenForo behavior outside the wiki.