[DanBC]

There are a bunch of plugins that provide collapsable comment threads.

[dredmorbius]

They don't work on numerous browser options, including Chrome on Android (which AFAIU doesn't support extensions), or, last I checked, Android.

It's a badly needed basic function.

[kwhitefoot]

This one works well on FF 45 on Linux: https://github.com/tomkel/hn-collapse.

But surely a GreaseMonkey script should be able to do the job too?