This practice is grammatically incorrect, because best is already the superlative of good. See examples of bestest used in a sentence. The meaning of bestest is best
How to use bestest in a sentence. But now they've stuck their necks on the line and revealed their bestest member. “bestest” is an adjective meaning “very best.” although it’s technically a word, it is considered nonstandard and should therefore be avoided in professional and academic contexts.
Extremely good (definition of bestest from the cambridge advanced learner's dictionary & thesaurus © cambridge university press) (nonstandard, informal, humorous or childish) best The best of the best It's my first time behind the wheel, but i'll do the bestest i can do!
Factsheet what does the word bestest mean There are four meanings listed in oed's entry for the word bestest See ‘meaning & use’ for definitions, usage, and quotation evidence. Discover the meaning of 'bestest,' its playful use in modern language, its etymology, and why it's not considered grammatically standard
Everything has to be the bestest, or he walks away But today, just for today, she seems to be on her bestest behaviour I mean, we're best friends now, the bestest friends in the world
