DAR-2366 DAR-2382 Fixes in EditPreview

Merging [DAR-2382](https://wikia-inc.atlassian.net/browse/DAR-2382) (edit summary bug fix) to [DAR-2366](https://wikia-inc.atlassian.net/browse/DAR-2366) (mainpage edit preview bug fixes) on @justnpT request.