You should probably mark different grammatical forms so that you have the definition you want for subsequent encounters with the word form. I often add the same basic definition for each word form, but the benefit of the LingQ system is to make fewer trips to phrase books and dictionaries and maximize your time spent with text. With proper names of things and places, it completely depends on whether I think the name or place is important. For example, I mark the forms of King Sejong because he’s an important historical figure and I want to read more information about him or atleast have it available. I don’t mark names of things that aren’t important to me and use the ignore button on them. The stats are great for measuring progress and giving yourself a sense of achievement, but don’t make them the focus of your LingQ usage unless you intend to use it as only a game.