I think (b) would be grammatically correct. But how about (a)? Would it be used?
(a) We talked about the movie which/that we saw before.
(b) We talked about the movie which/that we had seen before.
I think (b) would be grammatically correct. But how about (a)? Would it be used?
(a) We talked about the movie which/that we saw before.
(b) We talked about the movie which/that we had seen before.
Although there are undoubtedly some native speakers who might say (a), it is grammatically poor. The main (focal) part of the sentence ("we talked") is in plain past tense, so an event which occurred not immediately prior to, but some amount of time prior to the main event of the sentence (as indicated by "before") should be in the past perfect tense.
Thanks for the help, joadbres. Do you think we should avoid using (a)?
How about these pairs? Do you think that the first one should be avoided in each case?
(c) I saw this movie soon after I saw another.
(d) I saw this movie soon after I had seen another.
(e) He said Ann arrived on Monday.
(f) He said Ann had arrived on Monday.
(g) I lived in Osaka before I moved here in Kyoto.
(h) I had lived in Osaka before I moved here in Kyoto.