At Catholic Masses, only priests or deacons are supposed to read the Gospel readings (those from Matthew, Mark, Luke, and John), as opposed to the Old Testament readings and the NT Epistles or Book of Revelations.
If you are not Catholic, or are Catholic but don’t know or care about the rules, asking questions is fine. Asking sneering questions, on the other hand, is obnoxious. I don’t do that when it comes to other religions.
What is the harm in a regular person reading the Scripture in church?