Why does the backshifting of tenses rule not apply to this sentence?:
"I forgot what a liar he is."
Because the verb "forgot" in the main clause is past tense, shouldn't the verb in the noun clause ("is") be past tense, too?
Yet I see sentences like my example, which start with "I forgot" or "I had forgotten" and then use present-tense verbs, all the time.