well.. probably lots of people use another navigator, with different syntax at launching so.. can't i use opera for this?

NOTE: maybe a config file could help at this point. opera remote invocation looks like opera -remote openURL(URL,new-tab) but the complete list is here http://www.opera.com/docs/switches. of course an easy way to do it could be something like this at the config file:
OPEN_COMMAND=opera -rem.... %URL,... (so you only have to change the value of %URL when launching a request

and another question: which charset is used by default? i'm a spanish user and things like más (or similar) don't look great.. could the charset be selectable? (at the same way exposed for the first question i think)

regards

Well, actually since v0.1.3 the URLs open in KDE default browser be it opera, firefox, konqueror or whatever, you just need to set it in the Control Center. Still it's may be not a bad idea to add a config option to use a browser other than the default. I'll consider this for the next version 10x.
As far as the charset problem you mentioned, LTRSS was made specifically for LinuxTalks.org which is in English only so from that point of view there is no problem. However this in an issue of the parser which I didn't write and having a look at the code makes me think it will take a lot of work to make it suitable for other charsets. At this point I'm not planning to make such changes sorry :-( may be when I have more free time.

Best regards