I was unaware of this way to support micropayments. I have left my node with base 1 sat as that was the default and I was unsure if it was wise to got o zero. I wondered if there was a risk of my node getting spammed.
He only takes a percentage of the routed money. Most nodes take a percentage AND take a fixed amount. e.g. If I route 1 sat through most nodes, I'll pay 1 sat + 1% in fees. Through siggy's node, I'll pay only 1% in fees. Basically, it makes micropayments more economical.
The LN internally uses 1/1000th of a sat, but when you close a channel, you only get full sats. Having lots of micropayments (or fees) worth <1sat can add up, though.