Encara que el venedor no respongui, reemborsaran els diners.

Here encara que means even if or although, depending on context.

In this sentence, because the verb after it is in the subjunctive (respongui), the idea is closer to:

• even if the seller does not reply
• whether or not the seller replies

So the sentence means that the refund will happen regardless of the seller’s response.

Because encara que often takes the subjunctive when the situation is:

• uncertain
• hypothetical
• not yet confirmed
• irrelevant to the result

Here, the seller’s reply is not presented as a fact. The meaning is basically: even if the seller does not reply, the money will still be refunded.

That is why Catalan uses no respongui rather than an indicative form.

Respongui is the present subjunctive of respondre.

In this sentence it is third person singular, matching el venedor:

• que jo respongui
• que tu responguis
• que ell/ella respongui
• que nosaltres responguem
• que vosaltres respongueu
• que ells/elles responguin

So el venedor no respongui means the seller does not reply / may not reply in a subjunctive sense.

Yes, but the nuance changes.

• Encara que el venedor no respongui = even if the seller does not reply
  
  • hypothetical or uncertain
• Encara que el venedor no respon = although the seller is not replying
  
  • more factual, as if this is already known to be happening

So both can be possible, but they do not sound exactly the same. In your sentence, the subjunctive is the more natural choice.

Reemborsaran is the simple future of reemborsar.

It breaks down like this:

• infinitive: reemborsar
• future ending for they: -an
• result: reemborsaran = they will refund

So the main clause is in the future: they will refund the money.

The subject is an understood they.

Catalan often leaves out subject pronouns because the verb ending already shows the person:

• reemborsaran already means they will refund

So Catalan does not need to say ells reemborsaran unless the speaker wants extra emphasis or contrast.

In a sentence like this, the implied they is usually something like:

• the company
• customer service
• the platform
• the people handling the case

It is a normal, natural way to leave the agent unspecified.

Because Catalan normally uses the definite article with a specific countable noun.

Here el venedor means the seller, meaning the particular seller involved in the transaction.

Using just venedor here would sound incomplete or unnatural in normal prose. Catalan generally needs the article in this kind of sentence:

• el venedor
• la compradora
• el client

So this is simply the standard way to say the seller.

This is a very common learner question.

In Catalan, diners means money, but grammatically it is a plural noun. So Catalan says:

• els diners
• literally something like the monies
• but naturally just the money

That is why the verb would agree with it as plural in other sentences.

The article els is used here because we are talking about a specific sum of money already known from the situation: the money from the purchase or dispute.

Compare:

• Necessito diners = I need money
• Et tornaran els diners = They will give you back the money

Yes, it is correct and natural, especially in formal or customer-service language.

Common options include:

• reemborsar els diners = to refund the money
• retornar els diners = to return the money
• fer un reemborsament = to make a refund

Nuance:

• reemborsar sounds a bit more formal or administrative
• retornar els diners is often a bit more everyday

So reemborsaran els diners is a very good choice for a policy, platform, or support message.

Yes. You can also say:

Reemborsaran els diners encara que el venedor no respongui.

The meaning stays basically the same. The difference is mostly one of emphasis:

• Encara que el venedor no respongui, reemborsaran els diners.
  Emphasizes the condition first.
• Reemborsaran els diners encara que el venedor no respongui.
  Emphasizes the refund first.

Both are natural.

The comma separates the subordinate clause from the main clause because the encara que clause comes first:

• Encara que el venedor no respongui, reemborsaran els diners.

This is very normal in Catalan, just as in English.

If the order is reversed, the comma is often omitted:

• Reemborsaran els diners encara que el venedor no respongui.

So the comma is mainly about sentence structure and readability.