1) The fact that people care deeply about language is an unambiguously good thing! It's easy to explain why 'irregardless' is in the dictionary, and to show that the clear recommendation of the dictionary is:

"Use regardless instead."

2) It is instructive to observe that many people who seem to believe fervently that "words matter" don't seem to believe that "facts matter."

3) The problem people have with 'irregardless' is that it (obviously) is illogical.

This argument ignores the fact that the putative connection between morphology and logic is something that we impose upon language, not something that is inherent to language.

4) There is little logic to English words like 'biweekly' and 'inflammable,' for example.

Many people expect etymological logic to apply to morphology as well. If that were the case, 'December' could mean only and exactly "the tenth month." This is called etymological fallacy.

5) This lack of respect for logic bothers people only selectively. Sometimes there is good reason to say "very unique" or "I literally died laughing."

These are meaningful, expressive, and common ways to use these words; language can convey a rainbow's spectrum of hyperbole.

6) Recording these usages is the job of the dictionary.

Recommending them is not.

7) However, usage notes (as opposed to definitions) DO give recommendations! That's what they're for.

There are two kinds of facts presented in dictionaries: the lexical fact and the cultural fact.

The lexical fact includes conventional spellings, pronunciations, and meanings.

The cultural fact provides extralexical context for a word: Is it archaic? Obscene? Chiefly British? Informal? Offensive?

There is nothing inherent about a grouping of sounds or letters that can give us guidance about these factors. We use usage labels & notes for this purpose.

9) Using words in the real world requires negotiating these important cultural facts. We use words as building blocks in order to create nuanced meaning and narrative.

That means demonstrating a cultural awareness of how one's words will be understood by readers.

10) This cultural awareness is the manners of language.

Usage is the manners of language.

Manners are social. They have nothing to do with spelling or etymology. They are extralinguistic.

This is when we judge words by the company they keep.

11) Manners are social. Manners require judgment.

Manners can reflect education, class, region, prestige, taste.

Some of these judgments demonstrate care and thoughtfulness.

Some of them betray prejudice and cause offense.

A good dictionary will tell you the difference.

12) A word's inclusion in a dictionary is neither an endorsement nor a recommendation.

It is a plain statement of linguistic fact: This series of sounds and letters are understood by many people to mean a particular thing.

That's it.

BUT

13) If a word will cause embarrassment to you or offense to others, a good dictionary will give advice.

It's an owner's manual for language.

This usage advice comes in labels (offensive, archaic, technical, nonstandard...) and in notes that tell you what you need to know.

14) An enormous amount of research and care goes into the writing of dictionary entries.

The @MerriamWebster entry for 'irregardless' has BOTH a usage label ("nonstandard") AND a usage note.

The note concludes:

"Use 'regardless' instead."

/fin https://www.merriam-webster.com/dictionary/irregardless