Not to split hairs, but fornication, by definition, is sex between people who are not married to each other.  The post says they were married to each other, as opposed to married to other people.  Ergo, they were simply having sex as married people do (usually).

While agree the fact they were having sex in the unit, which apparently was raucous enough that it got them caught, adds to the "eww" factor, how does it speak to their moral character?