> don't ISPs detect these and ban

No. No ISP who desperately tries to grow marketshare at all costs and lock their customers into a year-long contract will intentionally ban users. I'm not even sure where this misconception comes from, it's not like ISPs led a massive PR campaign warning people of the dangers of running a server.

The only way you will get banned is if you cause disproportionate strain on their network, which means you'd need to exceed the usage of the typical gamer (downloading games worth hundreds of gigs regularly), streamer (streaming 4k video for hours at a time), cloud backup customer (uploading gigabytes regularly), Windows user (in its default configuration Windows can use P2P to share updates), torrenter (sustained full-duplex bandwidth usage), and unlucky idiot with a compromised device spewing DoS traffic at line-rate.

Saturate the pipe consistently for several days by hosting video? Yeah sure you could get a warning and eventually disconnected, assuming they don't already have traffic shaping solutions in place to just silently throttle you to an acceptable level and leave it up to you to move your homebrew YouTube clone elsewhere when you realize it's too slow.

Hosting a website which will have a few mbps worth of traffic with the occasional spike? That's a rounding error compared to your normal legitimate usage, so totally fine.

The reason most consumer ISPs have a clause against running servers (not even defining what counts as a server) is to preempt a potential business starting a data center off a collection of consumer connections and then bitching about it or demanding compensation when it goes down or they get cut off. Nobody cares about a technical user playing around and hosting a blog at home.