Is this usual? Check out this screenshot.
I've received 6GB and sent 2.4TB in just 10 days. Right now, I have 82 connections.
Doesn't seem to impact my internet speed, but it feels like a lot.
I have a 600Mbps symmetric connection with an average latency of 40ms.
It's normal for a full node that allows incoming connections. If you want to limit it, start Bitcoin Core with this option (in MB/day):
So this limits your upload to 100 GB per day.
I never cared for non-SI units
A bit of a nitpick here but the link says its unit is "MiB". Also in the Core's help menu says its default is uppercase "M" (1024base).
So, maxuploadtarget=100000 is about 104.8GB per day.
He can set it to 100000m if he want to set it to MB, not that it matters much though since it can exceed that by serving the latest blocks, mempool, etc.
Yes, the setting would have limit the ability of your node to help synchronize other Bitcoin nodes.
Its default value is "0" (unlimited), BTW.
Note: 82 connections isn't close to the maximum default connections of 125, so the stats in the screenshot may increase by 50% once it reached that.