To answer your questions, since nobody really has:
1. It's not secure to store passwords in your script editor-- however: there's no secure way to store passwords, really. Even if you did encrypt the password, you would have to encrypt it with some kind of key. In other words, guess how you would decrypt the password file? Yep-- another password. And both the encryption password and the encrypted password are stored on the same machine. Kind of useless if someone gains access to your drive, though it could deter some less knowledgeable hackers.
It's also important to note that though it's not secure to store passwords, it's also not secure, in general, to use passwords over IRC anyway. Everything on IRC is sent unencrypted unless you are connected via SSL, and even then, servers will likely not communicate via encrypted channels-- and even *then*, opers can easily gain access to data logs sent to service bots. In other words, even if you securely store your password, it's still easily accessible through different attack vectors-- arguably more likely attack vectors, since a hacking a random IRC user offers much less of a payoff than hacking an IRC server node itself.
2. Absolutely not. Proxies can easily slurp data-- I'd bet a bunch of them already do. Don't send sensitive info across proxies, in general. You should assume that someone is watching you when using these proxies.
So, to summarize: passwords over IRC are insecure period. It's a reality of the protocol-- the solution here is to, as Riamus mentioned, use throwaway passwords that you do not use anywhere else. If someone steals that password, the most they do is steal your IRC nick and possibly a channel or two for a few hours before opers correct the situation. So don't worry too much about it.
