Learn Hardcore Dutch: Die opmerking betekent niet dat hij boos is; haar opmerking is juist vriendelijk. - That remark does not mean that he is angry; her remark is actually friendly.

Because opmerking is a common-gender (de-) noun. For de-words in the singular, the demonstratives are deze (this) and die (that). Dat is used with het-words: e.g., dat huis. So: die opmerking, not dat opmerking.

Is die here a demonstrative or a relative pronoun?

A demonstrative. It points to a specific remark: die opmerking = that remark. As a relative pronoun, die would come after the noun and start a clause, e.g. de opmerking die hij maakte.

Why is niet placed after betekent? What changes if I move it?

Placing niet after betekent negates the meaning relationship: “does not mean that…”. If you say Die opmerking betekent dat hij niet boos is, you negate the adjective inside the subordinate clause (“means that he is not angry”). So the scope of niet changes the message.

Why is it dat hij boos is and not dat hij is boos?

Because dat introduces a subordinate clause. In Dutch subordinate clauses, the finite verb goes to the end: … dat hij boos is (not “… is boos”).

Can I drop dat like English often drops “that”?

No. In standard Dutch, dat is required in this kind of content clause: … betekent niet dat hij boos is. Omitting dat here is ungrammatical in careful Dutch.

What does juist mean here?

Here juist means “actually/indeed/rather,” signaling contrast with an expectation. It does not mean “correct” in this sentence. Compare: Het antwoord is juist (= correct) vs Haar opmerking is juist vriendelijk (= actually friendly).

Can I move juist? How does that change the emphasis?

Yes.

Haar opmerking is juist vriendelijk emphasizes the unexpected friendliness.
Juist haar opmerking is vriendelijk emphasizes that it is her remark in particular (and not someone else’s) that is friendly.

Why a semicolon here? Could I use something else?

The semicolon separates two closely related main clauses. Dutch also commonly uses a period or a comma with maar: …, maar haar opmerking is (juist) vriendelijk. After a semicolon, you do not capitalize the next word unless it’s a proper noun.

Do hij and haar refer to different people? And is haar ever “hair”?

Yes, they naturally refer to different people here: hij (he) and haar opmerking (her remark). Haar can mean “hair” only as a noun with an article: het haar. As a possessive before a noun (haar opmerking), it means “her.”

Why is there no article before haar opmerking?

Possessive determiners (mijn, jouw, zijn, haar, ons, jullie, hun) replace the article. So you say haar opmerking, not de haar opmerking.

Should there be a comma before dat?

No. Dutch does not normally place a comma before dat introducing a subordinate clause: … betekent niet dat … (no comma).

What’s the difference between betekenen and bedoelen?

betekenen = what a word/sign/remark “means” in the sense of its content or implication: Die opmerking betekent …
bedoelen = what a person “means/intends”: Zij bedoelt …
You’d use betekenen for the sentence you’re asking about.

How else can I say “does not mean (necessarily)”?

Common alternatives:

… wil niet zeggen dat …
… houdt niet in dat …
… impliceert niet dat …
To add “not necessarily,” insert per se: … betekent niet per se dat …

Could I use deze opmerking instead of die opmerking?

Yes, but it changes the deictic nuance. Deze = “this” (mentally/physically closer, just said/nearby), die = “that” (more distant or previously mentioned). Both are fine if that nuance fits your context.

Quick pronunciation tips for tricky words?

juist: the Dutch ui is a rounded diphthong; think “y” + “uh/oo” blended (approx “yuhst,” but more rounded).
boos: long “o” (bohs).
haar: long “aa” (haahr).
betekent: be-TAY-kent (unstressed first syllable).
opmerking: stress on the first syllable: OP-mer-king.