A question about SE
In the form used for an imaginary or hypothetical third person such as "Como se llega...?" How do you (does one) get to... what happens if the same sentence uses more than one verb? Do you have to continue using SE? For instance: Se piense que se conoce sus amigos... You (one) think(s) that you (he) know(s) your (his) friends...
3 Answers
Yes, you have to use as many ´se´ as verbs that require it.
Se suele responder que se utiliza el ´se´ siempre que el verbo así lo requiera
Now, in your example, uno piensa que conoce a sus amigos would be my Spanish version.
or... Se cree que se conoce a los amigos y luego se lleva uno grandes sorpresas.
Se piense que se conoce sus amigos... You (one) think(s) that you (he) know(s) your (his) friends...
If you are going to use this pseudo-passive Se, you have to say "piensa" in any case:
Se piensa que...
But now one would probably say "Se piensa que se conocen a los amigos" or any other of the good alternatives you've been given. Think of it: would you really say in a natural context:
It is though that friends are known.
Does that sound like a sentence you'd normally say? If it sounds like a natural sentence in English, I have no argument against it in Spanish, because it is the same thing.
but how come? If I am making a general statement, why use the TU form?
Are you one of those who believe that the grammar rules you read in books and web sites are as precise as Pythagoras' theorem? You use the passive reflexive SE for some general statements, but that doesn't mean that all general statements can be expressed with SE. If you think your language is more regular in this sense, you've never tried to teach English to a foreigner.
Mediterrunio is right, but the "se" doesn't fit in your sentence
Piensas que conoces a tus amigos.
Another example of "two verbs-two se":
¿Cuándo se supone que se van a abrir las puertas?