Apparent contradiction

Question

One of the model answers reads as follows          Mis amigos, que se llaman Luis y Mario, me visitarán mañana.Another explanation I have seen tells that when the pronoun is part of a phrase within brackets we should be using el que etc rather than just que.  I have fed  the sentence into the respected SpanishChecker with both alternatives and neither was identified as wrong.

Accepted Answer

Hola Peter
They are both right but they'll mean slightly different things. 
Mis amigos, que se llaman Luis y Mario, me visitarán mañana.
My friends, who are called Luis and Mario, will visit me tomorrow.
The clause using que, with commas, is not adding any extra information about the friends, it's just stating the names of these friends.
Mis amigos, los que se llaman Luis y Mario, me visitarán mañana.
My friends, the ones who are called Luis and Mario, will visit me tomorrow.
Here, the speaker is specifying who are specifically those friends who are visiting, it's going to be his two friends whose names are Luis and Mario, not the others (whoever they are) - it is identifying those two friends. 
The first one with only "que" is just saying "my friends, who, [by the way], are called Luis and Mario,...." - not picking two friends among a larger group. 
I hope this clarified it. Relatives are always tricky.
Saludos cordiales
Inma

Answer

Hola InmaI really can't see the difference between:Mis amigos, los que se llaman Luis y Mario, me visitarán mañana. (it is identifying those two friends.)andMis amigos que se llaman Luis and Mario me visitarán mañana. No commas. This surely is a 'relativa especificativa' and so identifies the friends.or would it be better just to sayMis amigos Luis and Mario me visitarán mañanaI'm really confused.Gracias