Merriam-Webster just legitimized "looksmaxxing" — but what does that teach a learner about register?

Band 8 writing requires you to match tone to task. Adding slang and internet abbreviations to the dictionary doesn't mean they belong in an essay or a formal email. The real skill is knowing when "cuffing season" is acceptable and when it will cost you a band score. Context awareness, not vocabulary size, is what separates a fluent user from a confused one.