In the first movement, Beethoven isolates the chromatic descending lines from the rest by placing them on the top staff, and, in doing so, uses five more ledger lines than if he had placed all the voices on the lower staff, as would have been normal for that time:
In the third movement, Beethoven is imitating a wind band or orchestra, so that the main melody lines are sandwiched in between accompaniment notes. He isolates the main melodies in the lower staff and the descant line on the top staff. At A the top line suddenly takes on a life of its own and descends stepwise back to the starting note of the main melody C

At the arrow, he suddenly changes the approach, possibly forced by the

When the passage recurs, he seems to have learned his lesson and doesn't make the same mistake, but is now forced to place the

The note placement was often extensively revised in later editions. Here is an older Peters edition. What an invitation to a massive, ugly, unvoiced performance of this movement: