Uses of "SE" : se discutió

Question

Can you see the difference between no. 6 and no. 7?
Are there any differences in meaning?
Could you please answer the questions below?

6, En el coloquio se discutió un tema interesante.

• 6a, In the symposium people discussed an interesting subject, OR In the symposium an interesting subject was discussed, (which one is correct?)
• 6b, tipo de SE: marca de impersonalidad o pasiva refleja (¿Cuál es correcto o ambos?)

7, En el coloquio se discutió de un tema interesante.

• 7a, In the symposium they argued with each other for an interesting subject.
• 7b, Tipo de "SE": con valor recíproco

Answer 1

According to RAE in this link:

discutir. ‘Contraponer opiniones sobre algo’. Puede ser transitivo: «Discutieron la conveniencia de comprar algunos libros de ocultismo» o intransitivo, caso en el que lleva un complemento con sobre, de o acerca de: «Discutieron de platos y de precios» ; «Un grupo de diplomáticos hipócritas discutían sobre la paz» (Jodorowsky Danza [Chile 2001]).

It means that:

• Discutir + sobre + something-> intransitive use
• Discutir + de + something-> intransitive use
• Discutir + acerca de + something-> intransitive use
• Discutir + something -> transitive use

So in your example:

6, En el coloquio se discutió un tema interesante.

In this first sentence as discutir is used in a transitive way and it is an example of passive voice (pasiva refleja) and it would be the same as saying this:

En el coloquio un tema interesante fue discutido

so it could be translated as: "In the symposium an interesting subject was discussed". Here "se" marks that this sentence is a passive voice (pasiva refleja).

On the other hand:

7, En el coloquio se discutió de un tema interesante.

This second sentence is an example of intransitive use of that verb because it's followed by the preposition "de". As it is instransitive then it can't be a passive voice.

I'd say that in this case it is an impersonal sentence. and its meaning would be something like: "In the symposium people discussed an interesting subject". Here "se" marks that this sentence is impersonal.