I think 建前 is similiar 'persona'.
It means not honesty, so tell 建前, sometimes it's lie from good faith.
For expample, if someone tell you "If you possible, please come to my house.", but sometimes it's not real answer. Just by courtesy.
I'm sorry to explain well(My English is not good).
I'm not Japanese, but I'm glad if my answer be help you. :)