Is this about the design patterns or the A*? Design patterns are a mix of techniques to pay complexity make code extensible that usually will not ever be extended and workarounds for the deficiencies of a specific family of languages. An example I posted about previously is that you could spend hundreds of lines across a dozen files implementing double dispatch, or you could use dramatically less if you aren't implementing it in terms of a language-provided dynamic-dispatch-on-the-first-argument-only primitive.

It is nice to write code that can be understood by the next reader. To explain what our invariants are and what we are up to, we have comments.