Open a comment with a list, for example: https://github.com/microsoft/PowerToys/pull/6979#issuecomment-707273901
Select one or more lines and drag them (but don’t put your cursor over the selected text, put it just to the right of it). The behaviour is buggy, you can drag other people’s lists (they thankfully don’t save). Dragging your own lists makes no sense, only one line is being moved around, even if multiple are selected.
Example video: https://imgur.com/a/IiEMNGd
Tested and confirmed buggy behaviour on 64-bit Windows 10 in Chrome 87.0.4280.88 and Edge Dev 88.0.705.9, both in normal and incognito mode.