Mikuji, you're my hero!
sevenlanguages? Do you speak them all fluently?
I am also very surprised to see that English is not your native language; you write it incredibly well (and no, I'm not patronizing you. I mean it!

) May I ask how long you've studied it and how? It's always been my goal with Japanese to speak it as well as I speak my native English; I'm trying to figure out how long that would take me and what I need to do to reach that level. I'd say it looks like you speak/write English on a native level: what did it take you to accomplish that?
I, too, am always glad to see other non-native Japanese who have mastered the language. I've been studying the language for almost three years now and there were so many times that I wanted to give up, thinking I just wasn't smart enough. People like Peter-san and my friends who already know Japanese have helped keep me going. I now think that all I need is a lot ( A LOT!) of practice and time and that I too will get a very good grasp on Japanese.
Finally, I too always get that comment from Japanese people. I think you have it spot on: they are mostly saying it in order to encourage you on a very hard path and to show appreciation for a non-Japanese learning Japanese (that doesn't happen too much). I also think they are empathizing with you, being that many Japanese study a second language (I have never respected foreigners more here in America until I seriously started studying this second language; I now know how hard it is and I know that any gains are significant ones and ones to be proud of). I remember when I was staying with a host family for a month in Japan that I constantly heard this out of politeness, but one time my Japanese host father was trying to speak to me in English and forgot a word and, under his breath, tried to remember the Japanese word. Somehow, I picked up what he was saying and provided the English translation. He looked at me in almost-shock and said, "You really ARE good at Japanese." (Even though I was a beginner; I had been only studying for some six months, but it was some rare word that I had just happened to luckily pick up). Scored me a few points though.
I'll now put in my piece about French from a Japanese perpsective:
My Japanese friend who speaks English too is also studying French. He says the pronunciation is a lot harder for him than English pronunciation. He thinks French grammar is a little easier in some ways. Ultimately, he like English better (he says this is probably because he has a lot of motivation to study English and already speaks it VERY well).