As a small experiment, I set the connections-per-torrent limit to 50 (it was at zero). Suddenly a torrent that was downloading at ~14KB/sec dropped to 0KB/sec. Apparently KTorrent decided to disconnect peers at random, instead of being a bit smarter and disconnecting the ones that weren't sending any data. Now, a couple of minutes later, it still isn't downloading any data for that torrent.

By the way, is it better to leave the limit at none and let KTorrent manage the number of connections per torrent, or should I set it to a certain number so KTorrent doesn't waste connections on useless peers?

KTorrent disconnects bad peers when peer limit is reached. Bad peers would be those with the lowest score with exception for the superseeders who also have low score.

Check out the score for peers and you should notice this behavior.

You have to get a pretty bad score to get kicked, so are you sure that this peer was kicked by KT ? The score has to be lower then -5.0 and higher then -50.0 (super seeders).

If the peer was your only downloader, there is no way he would have gotten a low score like that.

I'm sorry, I don't really have that information. Perhaps I'm wrong about all this, but it happened when I changed the connection limit, so I was thinking that maybe KT just dropped some to get within the limit. But since I haven't checked the source myself, I could be completely wrong about how it works. Sorry if I wasted your time on this one.