So this has been an annoyance for some time now in my game.

If someone accidentally highlights some text in chat, or if they click on a hyperlink image, their output window stops scrolling to show new output automatically. It'll stay where it is and they'll have to click around in the box a bit until they're not highlighting anything in order to get it moving correctly again.

Is there a way I can prevent this behavior? So that even if a player has something highlighted, the output still scrolls?
The control we have over what the output control does is very limited. The most we can do is focus and unfocus it, but I don't think that's going to help.

If you want that level of control over output, your only realistic option is to use a browser control instead. You will be able to detect things like the selecting of text using JavaScript, and scroll down if necessary.