The friend of Markku who came earlier and to whom we showed the house told us everything was fine, that the house was clean and warm. Markku and his son showed up very late that evening and left very early so we never had the chance to meet him. In fact we started preheating the house 3 days before this reservation and the house has been used already several weeks during this winter. Below is the one and only feedback, which was not meant to be arrogant or rude, that I wrote to Markku, (who was claiming a full refund of his stay).
Sorry to hear from your son's complaint. It's the first time in 5 years that I have a complaint like this. It's an old stone house as it shows in the picture that doesn't smell like a brand new hotel. Especial during winter season. Thanks for your advises anyway, we always take advises from our clients very seriously. However we will not compensate you for this reason, as we have not had a complaint from you or your friend, who has been there at 4 o'clock pm, during your stay at la Jaurie. I do hope you have a save and pleasant journey back to Finland.
The answer I got from Markku was of a nature that we decided not to respond anymore to him and to leave it to Airbnb to judge the situation, which was positive for us.