As to the question of "niceness," I disagree wholeheartedly. All the advice here is to use resources that are provided to all passengers.
Moreover, the person who makes it to the front of the line in the status quo has no moral superiority over others that somehow makes them more deserving of a convenient flight. Indeed, the reason someone would make it to the front of the line is typically a function of luck (they're seated nearer to the front of the plane, or they know exactly where the counter is because they fly through the airport often, or they're alone and in good health and therefore able to sprint to the counter faster than the elderly, disabled, and families).
By contrast, you actively do a service to your fellow passengers by using this article's methods: you don't take up a space in line that makes everyone else wait longer.
But if you're a believer in generalizability instead, consider this: If everyone followed this article's advice, everyone would be equally likely to get the best remaining seats (which seems ultimately the most fair allocation). But nobody would have to wait in long lines.