They are alternatives, but not necessarily improvements. "While I was reading your post" - this is exactly the situation that the past continuous is best suited for. While indicates a past action that serves as a backdrop for another past action, which is exactly what the past continuous expresses so clearly.
This is a phenomenon known as hypercorrection, when you take a perfectly acceptable sentence, misapply a rule, and turn it into something less harmonious or even incorrect. The most widespread example of hypercorrection is the misuse of "I". "Mommy, me and Bobby want..." "No dear, Bobby and I want. Bobby and *I*" So the kid says Bobby and I in every case when he wants to say "me and" even if it's an object and the me is absolutely essential. For the rest of his life. Which is why journalists and pastors and - God help us - teachers and writers come out with sentences like "She called Bobby and I in the morning." It burns us, preciouss, it burns.