Learn Hardcore German: Später kommentieren Fans im Internet das Turnier und schreiben einen langen Kommentar über unseren Höhepunkt im Spiel. - Later fans comment on the tournament on the internet and write a long comment about our highlight in the game.

the first “slot” is taken by Später (an adverb = “later”), so the verb kommentieren has to come next (second position), and the subject Fans is pushed after the verb.

Compare:

Fans kommentieren später im Internet das Turnier.
→ Subject first, verb second.
Später kommentieren Fans im Internet das Turnier.
→ Time word first, verb still second, subject moves after the verb.

So kommentieren before Fans is just the normal consequence of the V2 rule after putting Später at the beginning.

Why is there no article before Fans? Why not Die Fans?

Both are possible, but they mean slightly different things:

Fans kommentieren im Internet …
→ This is more like “fans (in general) comment on the internet …” or “some fans comment …”. It’s generic or indefinite.
Die Fans kommentieren im Internet …
→ This refers to a specific group, “the fans”, probably ones already known from the context (e.g. “our fans”, “the fans of that team”).

German can drop the article with plural nouns to express a non‑specific, general group, similar to English:

Teachers earn too little.
→ Lehrer verdienen zu wenig. (no article)

So in your sentence, Fans without an article just presents them as an unspecified group of fans.

What exactly is im in im Internet and im Spiel?

im is a contraction of the preposition in + the dative article dem:

in + dem = im

So:

im Internet = in dem Internet (“in the internet”)
im Spiel = in dem Spiel (“in the game”)

Both Internet and Spiel are neuter nouns:

nominative: das Internet, das Spiel
dative singular: dem Internet, dem Spiel

After in (with a location, not movement), German uses the dative case, so you get im Internet, im Spiel.

Why is it das Turnier here and not dem Turnier or den Turnier?

Turnier is a neuter noun:

nominative: das Turnier
accusative: das Turnier
dative: dem Turnier

In the sentence, das Turnier is the direct object of the verb kommentieren (“to comment on something”), so it’s in the accusative case.

For neuter nouns, nominative and accusative have the same form (das), so das Turnier is correct as the object.
dem Turnier would be dative, and den Turnier is simply wrong (you would only see den with masculine accusative or plural dative, but Turnier is singular neuter).

Why is it das Turnier kommentieren and not über das Turnier kommentieren?

In German, kommentieren is a transitive verb: it normally takes a direct object in the accusative:

Sie kommentieren das Turnier.
= They comment on the tournament.

You do not normally use über with kommentieren. The object comes directly after the verb.

If you want to use über, you usually change to a different structure, such as:

einen Kommentar über das Turnier schreiben
= “to write a comment about the tournament”

So:

kommentieren + Akkusativ → das Turnier kommentieren
einen Kommentar über + Akkusativ schreiben → einen Kommentar über das Turnier schreiben

The sentence starts with Später, but the verb is still in present tense (kommentieren, schreiben). Why not future tense?

German uses the present tense very often for future actions, especially when context or a time word makes the future meaning clear.

Here, Später (“later”) already shows this is about the future, so present tense is perfectly normal and very common:

Später kommentieren Fans im Internet das Turnier.
= “Later, fans comment on the tournament.” (understood as: will comment)

You could use the future tense:

Später werden Fans im Internet das Turnier kommentieren.

…but that often sounds more formal, heavier, or emphasizes the future more strongly. Native speakers usually just use the present + time adverb.

Why is it einen langen Kommentar and not ein langer Kommentar or something else?

Kommentar is masculine:

nominative: ein langer Kommentar
accusative: einen langen Kommentar

In the sentence, einen langen Kommentar is the direct object of schreiben (“to write something”), so it must be in the accusative.

Declension breakdown:

article: ein → einen (masculine accusative)
adjective: lang → langen (strong/weak ending according to the pattern)
noun: Kommentar

So:

Ein langer Kommentar ist langweilig.
(nominative: subject)
Sie schreiben einen langen Kommentar.
(accusative: direct object)

The sentence needs the second form.

What case is unseren Höhepunkt in, and why this form of unser?

Höhepunkt is masculine:

nominative: der Höhepunkt
accusative: den Höhepunkt

The preposition über in the sense of “about a topic” is normally used with the accusative:

über den Höhepunkt (“about the highlight”)

Now add the possessive unser‑ (“our”). Possessive adjectives are declined like ein:

Masculine singular:

nominative: unser Höhepunkt
accusative: unseren Höhepunkt

Since über here takes the accusative, you get:

über unseren Höhepunkt

So unseren is masculine accusative singular.

Does über always take the accusative in über unseren Höhepunkt im Spiel, or can it also take dative?

The preposition über can take accusative or dative, but the case depends on its meaning:

“over/above” in a spatial sense
- Accusative when there is movement toward a position:
  - Er fliegt über die Stadt. (He flies over the city.)
- Dative for a fixed location:
  - Die Lampe hängt über dem Tisch. (The lamp hangs over the table.)
“about/regarding” in an abstract or topic sense
→ Almost always accusative:
- Wir sprechen über das Spiel.
- Sie schreiben einen Kommentar über unseren Höhepunkt.

In your sentence, über means “about/regarding (a topic)”, so it uses the accusative: über unseren Höhepunkt.

Why is it im Spiel at the end and not just über unseren Höhepunkt?

Both would be grammatically correct, but im Spiel adds extra information: it specifies where/when this highlight happened:

einen langen Kommentar über unseren Höhepunkt
→ “a long comment about our highlight”
einen langen Kommentar über unseren Höhepunkt im Spiel
→ “a long comment about our highlight in the game”

Grammatically:

im = in + dem (dative)
Spiel is neuter → dative singular dem Spiel

Here im Spiel is a dative prepositional phrase indicating location/context of the highlight.

What’s the difference in nuance between kommentieren das Turnier and einen Kommentar über das Turnier schreiben?

They are close in meaning but have slightly different focus:

das Turnier kommentieren
- Uses the verb kommentieren directly.
- Focus is on the act of commenting itself, possibly in real time (e.g. live commentary) or as a general activity.
- Sounds a bit more compact and slightly more formal/technical.
einen Kommentar über das Turnier schreiben
- Literally “to write a comment about the tournament”.
- Focus is more on the product (a comment) and the act of writing.
- Feels a bit more concrete: you picture an online post, article, or long comment.

In your sentence, both appear:

They kommentieren the tournament (more general action),
and they schreiben einen langen Kommentar über the highlight (a specific written piece).

Using both is natural: first, a general verb for the activity, then a more specific description of how they comment.