I'd imagine the reason that it doesn't give an error when you append text to the end of an identifier is because of props. If a prop is invalid, the identifier will still return the value as if there wasn't a prop.
//echo -a $chan(#channelname).topic2
That will return the channel name rather than an error. If the prop isn't valid, it's removed. Of course, you could make it throw and error if there's no "." there. I'm just showing why it probably doesn't give an error.
