Learn Hardcore Finnish: Hän puhuu rehellisesti, vaikka se on vaikeaa. - He/She speaks honestly, even though it is difficult.

Finnish hän is gender‑neutral: it can mean he or she. The sentence does not say anything about the person’s gender. Context (or extra information) is needed if you really want to know whether it is a man or a woman.

Why is it puhuu and not puhua or puhun?

The verb is puhua (to speak). Finnish verbs change their ending according to the subject:

minä puhun – I speak
sinä puhut – you speak (singular)
hän puhuu – he / she speaks

So with hän, the correct present‑tense form is puhuu. Puhua is the infinitive (to speak), not a finite verb form.

How is rehellisesti formed, and is that a general pattern for adverbs?

Rehellisesti means honestly. It comes from the adjective rehellinen (honest).

Many Finnish manner adverbs are formed by taking the adjective stem and adding -sti:

nopea → nopeasti (fast → quickly)
selvä → selvästi (clear → clearly)
tarkka → tarkasti (precise → precisely)

So rehellinen → rehellisesti fits this common pattern. There are some irregular adverb forms in Finnish, but -sti is very productive and something you will see a lot.

What exactly does vaikka mean here? Is it although, even though, or even if?

In this sentence, vaikka means although / even though:

Hän puhuu rehellisesti, vaikka se on vaikeaa.
He / She speaks honestly, even though it is difficult.

Rough guidelines:

With a real, factual situation (as here), vaikka ≈ although / even though.
With a hypothetical situation, vaikka can be more like even if.

So here it is not hypothetical; it is a real difficulty, so although / even though is the best English equivalent.

Why is there a comma before vaikka?

Finnish uses a comma before many conjunctions that introduce a new clause, including vaikka, että, koska, mutta, and others.

Here we have two clauses:

Hän puhuu rehellisesti – main clause
vaikka se on vaikeaa – subordinate clause introduced by vaikka

Because the second clause is attached with vaikka, Finnish punctuation rules require a comma before it. This is more systematic than in English, where the comma before although / even though is sometimes optional.

Why does the second clause use se instead of repeating hän?

In standard written Finnish, hän refers to a person (he / she), while se usually refers to it / that (a thing, situation, or previously mentioned action).

In this sentence:

Hän = the person
se = the act of speaking honestly / the situation

So vaikka se on vaikeaa means although it is difficult (to do that), where it points back to speaking honestly.

If you wrote vaikka hän on vaikea, it would change the meaning to although he/she is difficult, which is not what is intended here.

Note: in colloquial spoken Finnish people often use se for people too, but then they would normally say Se puhuu rehellisesti, vaikka se on vaikeeta (using se both times). The given sentence is in a more standard style.

Could you leave out se and just say vaikka on vaikeaa?

Yes, that is possible and grammatical:

Hän puhuu rehellisesti, vaikka on vaikeaa.

Here on vaikeaa works like an impersonal it is difficult, without an explicit se. Finnish often allows such subjectless clauses.

Nuance:

vaikka se on vaikeaa explicitly points to that thing (speaking honestly).
vaikka on vaikeaa is a bit more impersonal or general: although it is difficult (in general).

Both are fine; using se connects the difficulty more clearly to the specific action mentioned in the first clause.

Why is it vaikeaa and not vaikea?

Vaikeaa is the partitive singular of vaikea (difficult).

In sentences that evaluate an action or general situation, Finnish very often uses the partitive for the complement:

On vaikeaa puhua rehellisesti. – It is difficult to speak honestly.
On hauskaa matkustaa. – It is fun to travel.
On tylsää odottaa. – It is boring to wait.

Your sentence is really just a rearranged form of:

Puhua rehellisesti on vaikeaa. – To speak honestly is difficult.

In this type of structure (commenting on an activity, not a concrete countable thing), the adjective commonly appears in partitive singular (vaikeaa, hauskaa, tylsää).

If you describe a concrete noun as difficult, you normally use the nominative:

Tehtävä on vaikea. – The task is difficult.

So:

Se on vaikeaa. – It (doing that) is difficult.
Tehtävä on vaikea. – The task is difficult.

Is there a more literal Finnish version like Puhua rehellisesti on vaikeaa, and how is it related to this sentence?

Yes:

Puhua rehellisesti on vaikeaa. – To speak honestly is difficult.

Your original sentence:

Hän puhuu rehellisesti, vaikka se on vaikeaa.

is conceptually:

Hän puhuu rehellisesti, vaikka puhua rehellisesti on vaikeaa.
(He speaks honestly, although to speak honestly is difficult.)

Instead of repeating puhua rehellisesti, Finnish replaces it with se, giving the smoother and more natural vaikka se on vaikeaa. So the two structures are closely related, and vaikeaa appears in both because it is commenting on an activity, not on a concrete noun.

Can I reverse the clause order and say Vaikka se on vaikeaa, hän puhuu rehellisesti?

Yes, absolutely:

Vaikka se on vaikeaa, hän puhuu rehellisesti.

This is perfectly grammatical and means the same thing. The difference is only in emphasis and flow:

Hän puhuu rehellisesti, vaikka se on vaikeaa.
→ starts with what he/she does, then adds the contrast.
Vaikka se on vaikeaa, hän puhuu rehellisesti.
→ starts by highlighting the difficulty, then shows what he/she still does.

Both orders are natural in Finnish.

How would the sentence change in the past tense?

To put it into the simple past (imperfect) in Finnish, both verbs go into the past:

Hän puhui rehellisesti, vaikka se oli vaikeaa.
– He / She spoke honestly, although it was difficult.

Changes:

puhuu → puhui (past of puhua)
on → oli (past of olla)
hän, se, rehellisesti, vaikeaa stay the same

The structure and the use of vaikka and vaikeaa do not change; only the verb tense changes.