I guess I was thinking primarily of the example given where it it is absolutely not correct to put in the prefix Lord for someone who was simply a lord of the manor.
The courtesy titles of Lord and Lady for younger sons and daughters of Dukes and Marquesse is certainly correct, however, I am not sure we should be using them in the medieval period when I am not sure the practice was in effect. It just adds to the confusion of who should be called Lord, as in this case.
We do not put Lord of (the manor) X in the nickname field. Only actual peerage titles should go here (King, Duke, Marquess, Earl, Viscount, Baron, etc.). Many of not most pre-1500 individuals held several (up to dozens) of manors. It's silly to put 'Lord of' for all of them. They are simply land holdings held by feudal tenancy. They are an important part of a person's biography because records relating to land holdings (IPMs, feudal aids, feets of fines, charters and grants) are the primary way of tracing medieval lines of descents, but they don't belong in the nickname field.