Please post your nominations for Best of Code Review 2013 — Diplomat category: Tough advice in an answer, delivered in the most tactful manner.
In your nomination post, be sure to include a link to the answer, as well as a short justification. One nomination per post, please. Answers being nominated must date from 2013.
First Java program critique (Game of Life)
@rolfl started with some encouraging words for a beginner, followed by a few thought-provoking questions, and finished by giving away some (but not too much) code that could be used to vastly simplify the solution. Very well written, in my opinion.
Elias did a good job explaining why the OPs' idea is essentially not very useful and what the shortcomings are.
Typesafe Java properties with events and runtime reflection
It is not easy to tell someone that "What you have written here does not seem very useful at all". I did my best in explaining why that was my opinion, and what other approaches to use instead.