I'm not sure if this is a bug, or if it's by design, but if you are connected to two servers, and type the following in one of the windows of the first connection:

//scid 2 echo -a Debug

It echoes in the active connection's (1) active window rather than connection 2's active window.

If this is not a bug, then can someone please tell me how to echo a specified connection ID's active window?

Here's what I use

//echo $iif($cid == $activecid,-a,-s) <text>

~ Edit ~
Sorry, no I don't think it's a bug. -a echos to the active
window whether the originating connection is the active
connection or not. It's the intended behavior IMO, as it
should be, also IMO.

Not really. By definition -a means "active window". There is only ever 1 active window and that is the one you're looking at.

Typing /scon -a echo -a hi will return N results in the same window, N depends on how many connections you have open. They're all echo'd to the same window because it can only echo to 1 window, the active one.

It's not really a bug, the original command could just be interepted to work in different ways.