I agree with you ivan667. Lists would be a powerful edition to this script but I will have to find some time to make these changes.
As for the multi-line edit box at the bottom of the @twitter window, I asked over a hundred people if their edit box would hold 140 characters and about 40% said no. The issue isn't that their screen is too small. It's just that many people don't use mIRC in full screen, but rather in a cascaded style with multiple windows on the screen.
If you want the single line editbox , just do a find and replace on the script:
Find:

window -E

Replace with:

window -e