Is the word comentário the same in Brazilian and European Portuguese?

Yes

The word "comentário" is identical in meaning, spelling, and grammar in both Brazilian and Continental Portuguese. The only difference is in pronunciation.

In Brazilian Portuguese, the vowels are generally more "open" and clearly articulated, making the syllables easier to distinguish. In Continental Portuguese, there is a strong tendency toward vowel reduction. This means that the unstressed "e" in "comentário" is often pronounced very shortly or becomes almost silent, resulting in a more "closed" and condensed sound.

Brazilian Portuguese Examples

1. Deixe seu comentário abaixo. (Leave your comment below.)
2. Não concordo com esse comentário. (I don't agree with that comment.)
3. Li todos os comentários no YouTube. (I read all the comments on YouTube.)
4. Aquele comentário foi muito grosseiro. (That comment was very rude.)
5. Fiquei sem palavras para o seu comentário. (I was speechless at your comment.)

Continental Portuguese Examples

1. Deixa o teu comentário abaixo. (Leave your comment below.)
2. Não concordo com esse comentário. (I don't agree with that comment.)
3. Li todos os comentários no YouTube. (I read all the comments on YouTube.)
4. Aquele comentário foi bastante rude. (That comment was quite rude.)
5. Fiquei sem palavras perante o teu comentário. (I was speechless at your comment.)