Smyth #325a says: The enclitic forms MOU, MOI, ME; SOU SOI SE are used
when the pronoun is unemphatic . . .
Robertson Pages 286 and 682, agrees with this but with major qualifications.
He states that the enclitic form some times appears to be emphatic. He also
is hyper cautious about determining whether SOU is enclitic or not.
Conclusion: Generally speaking the enclitic form is unemphatic, but not
always. Determining whether SOU is enclitic or not from a unical manuscript
is problematic. Therefor no reliable inference can be drawn from this data in
John 4:18.
Clay Bartholomew
Three Tree Point