Official message now on MH.com on 6 Feb:
Entry Restrictions Due To Coronavirus
Due to travel restrictions imposed by certain countries upon visitors to (sic? should this be "from" and not "to"?) Mainland China, Hong Kong, Macau and Taiwan within the last 14 days, Malaysia Airlines passengers will not be allowed to check in for their travel into the respective countries... and proceed to list out 18 countries (to date). Passengers who are affected by this entry restrictions will be eligible for a full refund/ rebooking for tickets purchased on and before 6 February 2020 for travel dates on 5 February 2020 to 29 February 2020.