Learn Hardcore Russian: Не стоит спорить в чате, когда можно спокойно поговорить по телефону. - It’s not worth arguing in the chat when you can calmly talk on the phone.

Не стоит + infinitive is an impersonal construction meaning “it’s not worth (doing)” / “you shouldn’t (do)”.
There’s no subject because Russian often expresses general advice impersonally:

Не стоит спорить = “It’s not worth arguing” / “Don’t argue (it’s a bad idea).”

It’s softer/more “reasonable-sounding” than a direct command.

How is не стоит different from не надо or нельзя?

They overlap, but the nuance changes:

Не стоит = “not worth it” (advice based on practicality/benefit).
Не надо = “don’t” / “no need to” (more direct, often practical or parental).
Нельзя = “must not / not allowed / impossible” (prohibition or impossibility).

So Не стоит спорить… suggests: arguing is pointless compared to a better alternative.

Why is спорить in the infinitive, and what aspect is it?

After не стоит, Russian uses the infinitive: не стоит + (что делать?).
Спорить is imperfective, describing the activity in general (arguing as a process/habit), which fits general advice.

Could I say не стоит поспорить instead?

Usually no in this sentence. Поспорить is perfective and often means “to have an argument (for a while / once)”. With advice like this, Russian typically uses the imperfective (спорить) to mean “don’t engage in arguing (as an activity)”.

You might see perfective in other contexts, but here спорить is the natural choice.

Why is it в чате (with в)—could it be на чате?

The normal collocation is в чате: you’re “inside” a chat space, like в комнате, в группе.
На чате sounds unnatural for most speakers (though в чате and в чате/в чатике are common; на is used for things like на сайте, на форуме more often).

What case is в чате, and why?

В чате uses the prepositional case because в answers “where?” (где?) when it means location:

в чате (Prep.) = “in the chat”

(If it were motion “into,” it would be accusative: в чат.)

What does когда mean here—“when” or “if/since”?

Here когда is closer to “when/since” in the sense of “given that a better option exists”:

“Don’t argue in chat, when you can calmly talk on the phone.”

In English it can feel like “when = if,” and Russian also could use если:

…если можно спокойно поговорить по телефону. Both work; когда often sounds more rhetorical: “why do X when you can do Y?”

Why does the sentence use можно?

Можно + infinitive is another impersonal pattern meaning “it’s possible / you can”:

можно поговорить = “it’s possible to talk / you can talk”

It’s neutral and common for general statements and suggestions.

Why is it поговорить and not говорить?

Поговорить is perfective and usually means “to have a talk (for a bit), have a conversation”—a complete event.
Говорить is imperfective and means “to speak/talk” as an ongoing activity or general ability.

So спокойно поговорить по телефону = “have a calm conversation on the phone (instead).”

Why is it по телефону and not в телефоне or через телефон?

The standard Russian way to say “by phone / on the phone” is по телефону (preposition по + dative):

по телефону (Dat.) = “on the phone / by telephone”

В телефоне would mean “inside the phone” (physically or “in the device”).
Через телефон can mean “via the phone” in a more technical/mediated sense, but it’s not the default for calling.

Why is there a comma before когда?

Because когда можно спокойно поговорить по телефону is a subordinate clause. In Russian, subordinate clauses introduced by words like когда, если, потому что, который are normally separated by a comma:

Не стоит спорить в чате, когда…