This has some puzzling elements. The phenomenon of a ‘rogue owner’ with ” … a habit of renovating properties with little regard to the neighbours” is, sadly, not unfamiliar. They are often good at making all the right noises about giving notice etc, but the resonant surfaces suddenly appear, and then the ‘for sale’ notice goes up with all the superficial glamour of what may really have been a ‘quick and dirty’ reno laid out the the advertising brochure.
Surely, from this point, it is ‘caveat emptor’ — it is not the responsibility of the Owners’ Corporation to reverse changes that are in conflict with by-laws — or just plain anti-social — made without its consent or knowledge. If a purchaser has suddenly found himself committed to expensive internal changes, it is unfortunate. However, ‘due diligence’ in checking strata records plus, if possible, some discreet informal contact with existing owners could help ensure the would-be purchaser is properly informed.
If, as MsM appears to be suggesting, there has been some collusion between, on the one hand, an agent looking to snap up a property for himself instead of seeking the best price for his vendor client and, on the other hand, a strata manager looking to help a mate work a cosy deal at the expense of the owners paying him to look after their interests, then it is a cause for grave concern. You would have to get the facts very well documented. It could be a case for criminal, rather than strata, law.