For a few years I've made it a personal point not to read any political coverage with overblown action verbs in the title like "X slams Y over spending bill" or "Y attacks Z". It's subjective but I swear it has genuinely helped my mental health. A filter that does this would definitely be nice now that you mention it!
You can block the whole Fediverse community. I did. Like, it's helpful. I also blocked asklemmy. Also helpful. I haven't blocked it on kbin, though. It doesn't matter, I see shit I'm not subscribed to when I filter by "subscribed" still. I think filtering by keyword is going to be a long time away. You can be obnoxious as a commenter, though. When you see the keyword, say something contrary in a comment. That could be fun.
It will be so important once US election cycle comes around. It became a game of wack a mole individually blocking subreddits versus just setting relevant keywords to make the reddit viewing experience wonderful as opposed to a rage inducing. We need a Fediverse Enhancement Suite.
I'm not a Connect dev and the app is not open source yet, so I can't quantitatively give you an answer. As a user, it's been working fine for me on all feeds.
I recommend posting something in the Connect for Lemmy community. If a feature is broken, the dev probably wants to hear about it.
I would love for this to be a feature, I want to filter out any posts that could be a trigger like sexual assault. I could do it in the reddit third party apps.
You can block communities and magazines that focus on it, which should get rid of the lion's share of Reddit-related content. It's been a bit disappointing to see so much low-effort, choir-preaching memes and content flood in. Hopefully the Fediverse can progress to a place where the primary activities extend beyond discussing the Fediverse & Reddit.