I go with the 1/4th rule as well, but it needs to be monitored for sure. If it's actually distracting you from your work then you might want to switch to podcasts or any other content that doesn't need your full attention. Watching movies or tv-shows on there I'd say it's not okay. It's def worse during the boring periods…
I did it a lot at almost every studio I worked in. It would rarely be bigger than 1/4th of my screen (if even) and, most importantly, don't let it interfere with you getting shit done. Most of the time I'm not really 'watching' anything so much as just having something in the background to listen to and glance at every now…