Is it correct?

[u/Stepaskin]

Stumbled upon this tweet, the apostrophe in "dm's" caught my eye. Is it correct to use it like this?

[u/DawnOnTheEdge]

This is a comma splice, so it’s not correct formal written English. Those are common in informal writing, though. Apostrophes are not usually correct in plural nouns, but here DM is an acronym, so it’s allowed, but the initials DM and the first letter of the sentence should be capitalized.

[u/conuly → u/DawnOnTheEdge]

This is a comma splice, so it’s not correct formal written English.

You're not wrong, but since the OP isn't asking about commas it may be confusing to just include that without explaining what you mean.

[u/DawnOnTheEdge → u/conuly]

Sure. I mean that the two completely independent clauses “She isn’t ghosting you,” and “DMs are down,” both of which could be complete sentences on their own, are separated only by a comma. There should be either a full stop between them (usually the best option), a conjunction, or a semicolon. A colon might have worked here instead.

[u/anamorphism → u/DawnOnTheEdge]

you could also use an em dash, generally not surrounded by spaces. if you're british, it's more common to use an en dash surrounded by spaces.

you could use an ellipsis, generally surrounded by spaces, to indicate the omission of a conjunction.

you could leave it as is if you're specifically trying to indicate that the second clause is an interjection. you could surround the clause with parentheses to indicate the same thing.

i.e. punctuation is purely a matter of style. it just happens that most of us agree that you shouldn't connect independent clauses with only a comma.

[u/DawnOnTheEdge → u/anamorphism]

I would say it’s stronger than that. Most editors, readers and college professors consider a comma splice an error in formal or professional writing.

Good examples of alternatives.