I, like you, am going from memory, and it might not be absolutely accurate. You could have said something like the scribes taught the Torah sitting in Moses seat, but read is what I remember, and that had been puzzling me because it didn't quite seem to match what I perceived from other places.

Trying not to overdo it with seeing current practices in NT synagogue worship, when I read the Luke 4 passage I think that they had a tradition of standing to read scripture, then sitting to discuss it, similar to the one today. Since the reader chose the passage, he must want to discuss that passage, and it would seem there was a custom of letting the reader make the opening remark. When it records “And the eyes of all in the synagogue were fixed on him” I think this is because they were waiting on Jesus to start the discussion. Who knows, he could even have paused for a short time after sitting down to let anticipation build a bit, so people were paying closer attention and would not miss what he was telling them.

Then, of course, when they heard his comments they reacted to them. But that's beyond my standing while reading question.