I just block them using ublock origin, right click -> block element.
One problem is that often, those forms insert a "overflow: hidden" into either <body> or <html>, meaning the page cannot scroll anymore. Twitter does this too.
It's possible to just remove it with the dev tools, but it's quite annoying.
I've asked ublock for a way to fix this, like:
##body,html:matches-css(overflow: hidden):style(overflow:auto !important)
But it doesn't really work.