I would like to have 2 DL/UL counters: a global one and a session one.

The session one is what we have already. What would be nice is another counter that shows the total data transfer and share ratio since install.

I am using ktorrent from ubuntu repos, version 4.0.3.

Some upgrade ago (2 years or more) This feature was installed by default, now I would be happy to find a plugin doing this

There was never such a feature

Strange, at some point, when I restarted Ktorrent (2.x?? maybe 3.x??) the counters would not clear, and would continue from the previous session.

It may have been a bug. It is just hard sometimes to make bugs apart from features unless you are involved in development