Does a low user-set maximum upload speed translate to slower download speeds in µTorrent?

This question has been asked numerous times on the web and the given answer almost always is yes. However, I never saw any support and I suspect that the answer is given purely to give the motivation for people to seed.

I am not aware of any automatic fairness system that takes place over the torrent protocol. It is probably possible for users to block others who they deem to be not generous enough, but does the torrent network already discriminate against people who set low limits for upload?

It's clearly the case that an unrestricted maximum upload speed can hamper download speeds and most of the time it is recommended that one set the limit at 80%-90% of the capacity, but this question deals with setting the upload speed too low, not too high.

There is a sort of fairness system - BitTorrent uses a choking algorithm to handle congestion and prevent this kind of thing. I don't know exactly how it works, but it ensures that connections to users who upload more are prioritized. If your client does not receive any piece of the file from a particular peer, the peer may be snubbed.

More information.

Using uTorrent on 2014 Macbook Air.

When my uploads are limited to 1kbps, my download speed is almost always 100kbps or lower.

When I removed upload limits, my download speed immediately increased to 2.5mbps

It would appear that in my case, upload speed absolutely affects download speed.

I've recently been thinking about this as well. A quick test of a download I was engaged in with µTorrent gave me these results.

Limited to 1 kbps upload gave: 10 - 50 kbps download.

With the download still running I change to this.

Unlimited upload speed gave: 4 - 8 mgps download.