To further explain the joke: note the contrast between the title, which crams in more words than can comfortably fit, with the body, which neatly expresses the advised course of action. An explanation that is more communicative but less literary would go as follows:

The word "rational," particularly when in the phrase "most rational," is seen as contentless and will cause downvotes and highly upvoted complaining comments. If you want advice on what toothbrush to buy, shoes to wear, or diet to eat, ask for advice and state your objectives. A 'rational' toothbrush is one that best acquires some value- and so just target that value. If you write a post asking for advice on improving your oral heath, you might get a recommendation for a flosser which could do more than getting a slightly better toothbrush.

See also the particularly rational brand of cigarettes.