Learn English – May “by the way” be used in formal professional writing

The usual wording of this idiom is "the pot calling the kettle black". The idea is that the pot is black itself, so it is not in the position of being able to accuse the kettle of being black. A very similar idiom you will probably be familiar with is "he who lives in a glass house shouldn't throw stones [at others]", or any variations thereof. Wikipedia has more similar idioms still.

The pot-kettle situation is a shorthand to refer to that idiom. It is not a common shorthand, so you won't find it in a dictionary. It is just a hint by this particular author at the actual idiom.

Long form: Thanks. Feel free to contact me as well if you have any questions.

Short form: Thanks. Same to you. (assuming the forum is an informal environment)

However, on many forums, you might want avoid such chit-chat since it's implied in the forum environment.