Torrent trackers usually automatically add 'retracker.local' to a tracker list.
retracker.local is a popular host name for local tracker server. Currently only a few small internet providers have own tracker servers in their WAN, so it may be useless for user and generate unnecesary traffic. Even worse - provider can set up such local tracker server but with only one purpose - spying on its users activity.

My suggestion is to give KTorrent users a setting that allows them to disable retracker.local in list of active trackers for all existing torrents and automatically disable it for all new torrents. Currently I have to do this manually each time I add a new torrent.
Best of all is to not just block retracker.local but block all tracker servers from specified black list based on name templates. Or all except specified in a white list. This could help to secure leakage of confidential info about KTorrent users activity.