This drives me nuts:
When I'm using preaty much any other program on my computer, I like to use the "home", "end" and arrow keys to navigate lines of text. I'm one of those people who finds it annoying to have to switch frequently between the mouse and the keyboard.
In SL, this works just fine, for IM, notecard writing and editing scripts.
What it doesn't work for is regular in-world chat. I know this is because home and the arrow keys are mapped to avitar movement, but it's more annoying than it's worth. I'm very typo-prone. If I've typed in chat beyond the length of the window, this layout makes it *impossible* to go back and fix a mistake at the begining of my sentance.
This could be fixed by something as simple as, oh, needing to hit 'Tab' to bring up a chat prompt each time and then effectively having the keys be in "text edit mode" untill you hit enter or toggle it off again with Tab or Escape (this is just an example from another computer game.) It's not like anyone can already move and talk at the same time...I don't think anyone is dexterous enough to acomplish that. ^.^