I just made the classic mistake of booking a flight on the MH site but I typed in May 6th rather than May 5th. I only noticed once my ticket was issued. I immediately noticed it and so I called MH within minutes of booking to ask them to switch the dates. AND OF COURSE the answer was - $100 USD change fee as per ticket rules. It was only a $86 ticket. RRRRR! There was no way MH was going to change it.
This is why I will ONLY book on US Websites as they have the 24hr cancellation / change rule.
How I hate MH sometimes. So inflexible.