What specifically is allowed?

[Jabberie]

That's not doing what you said it does. It's not checking if you are over a character portrait. If it was, that would be interacting with the game in a bad way.

It's simply checking if you are over a certain section of the screen. You're making an overlay essentially.

Perhaps I am being a bit too paranoid about basic multiboxing functionality.

My example is a snippet from HotKeyNet script that checks if the mouse is over a character portrait in game. Such that I can click/type a hotkey while the cursor is over a window region and have it trigger a corresponding macro to heal that specific group member on my healer.

<HotKey ScrollLockOn Button5>
    <If MouseIsOverWindowRect WoW1 28 30 224 57>
        <SendLabel w2>
            <Key Alt 1>
    <Else If MouseIsOverWindowRect WoW1 18 165 136 40>
        <SendLabel w2>
            <Key Alt 2>
    <Else If MouseIsOverWindowRect WoW1 18 240 136 40>
        <SendLabel w2>
            <Key Alt 3>
    <Else If MouseIsOverWindowRect WoW1 18 315 136 40>
        <SendLabel w2>
            <Key Alt 4>
    <Else If MouseIsOverWindowRect WoW1 18 390 136 40>
        <SendLabel w2>
            <Key Alt 5>
    <Else>
        <SendFocusWin>
            <Key %Trigger%>