I also find the small amount of code presented annoying - the entire screen is constantly scrolling up & down on me as I mouse-roll thru code.
I made a big fuss when the code box had no limit and I am quite happy with it now because I use the select button and copy the code to my text editor which I find much easier to work with. No matter the size of the code box it lacks (and always did lack) the ability to highlight words and to mark the ends of functions.
When I first look at a Post I am much more interested to get the OP's comments (which are often above and below the code) before deciding whether to look at the code.
Obviously I have no objection to a reasonable increase in the size - but if it goes more than double what it is now I reckon it will become unwieldy.
If it is possible to leave its present size and re-enable the ability to manually expand it maybe everyone would be happy.