I think it all depends really.
I only play on servers of respect and honour. And I don't care if people think that sounds silly, once you get into it its far more fun. Saber fights one on one with no force etc. it rocks.
Anyway, I rekon if your in a server like that, then attacking someone who has the Saber down or is typing is real lame as its not whats expected in that server, hell, if you attack two people saber fighting together, your out of order on a server like that. In servers like that the score board has no meaning, infact it often happens that the best players are at the bottom.
Where-as on a "normal" FFA server, those "rules" do not aply as people are playing differently, so attacking someone when there saber is down is more acceptable.
So it really depends on what server you are playing on.
However, I personly would never attack someone when they are typing, but thats just me. I think getting points in like that s just a waste and I'll not feel like I have earned the position I get because of it, it'd just be cos I was lucky to see somone who couldn't attack back. In fact I'd never attack someone with there saber down in a normal FFA unless I could tell thats how they fought.
it really is all very dependant on what server you play on. If you do something deliberately against what is acceptable on that server, then your lame and just ruining other peoples fun. But if its acceptaed by the majority on the server, then there is no problem.