Sidney lives in a men's boarding house on Capital Hill. When he isn't
trolling USENET on his old donated computer, he's outside smoking
cigarettes with other old drunks and crack addicts who would be
homeless if the rent wasn't so cheap.

He is not a danger to anyone. He mostly just watches people walk by
silently while taking a drag and contemplating his boring life.

Though Sidney is a strict vegetarian, he is in poor frail health due
to his habits and mental disability.

Trolling is Sidney's life. He feels he has never accomplished anything
though he could have been a great musician. Trolling the Internet
gives him his sense of self worth. On the Internet, he can pretend to
be the best at everything. This helps him to deal with his mental
problems.

And Sidney is probably not a crack addict. They only live for about 2
years in Seattle. Sidney might have other addictions which may account
for his mental problems.