Originally Posted by konungursvia
'I thought I replied' is common in speech, so no one can call it wrong. Having said that, when you are attempting to use written English correctly, you must write "I thought I had replied" in this case. The others are not correct in terms of the norms of formal written English. Only in vernacular spoken English.
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Hi again, Kon. I just wanted to add one more thing. It seems to me that a suggestion that some structure must be used for FWE/SWE and others forsaken, takes away from those writers the opportunity to say what they may want to say in English.
Just because someone compares two similar collocations, finds one to be more formal and then pronounces that that's the only allowable one for SWE/FWE is to my mind an untenable situation.
Again, this isn't a collocation that would find great use in SWE but regardless, if I'm writing to someone and I don't feel that greater formality is due them, I'm certainly not going to opt for the past perfect.
I just can't understand why you would it think it appropriate/a good thing to tie the hands of writers by excluding certain structures/collocations.

English Teacher