Refere to your 1st question: The comma makes different. The command /join #chan1,#chan2,#chan3.. is used to join multiple channels at the same time, but unfortunately /join 0 will return to part all channels instead. In your case, /join #2,000, that mean you joined Channel #2 and after that you joined 0 and that will return to part all channels.
For your 2nd question, I'm not sure what is wrong. Why don't you just ask them to type /join #...::LDS::... ?
