Hi @Ата. Thanks for sharing your thoughts! I have a suggestion that may solve one of your problems.
It looks like one thing uk.wiki is using the Recentchangestext field for is to put announcements inside the "Other review tools" box. But there is another field that will put announcements OUTSIDE, and above, the box. It's called Recentchanges-summary, and can be customized at Mediawiki:Recentchanges-summary.
Using this field for high-value announcements makes good sense, I think. Our research shows that most of the links in these boxes are never used. And, as you know, many users don't like it when search results are pushed down, as they are pretty significantly by these links.
So, this technique lets you make distinctions between the things the community wants everyone to see—and which truly earn their spot at the top of the page—versus the things that may be useful for some people some of the time. Using Recentchanges-summary will enable you to get the best of both worlds: important messages are prominently displayed, but the page is decluttered and vertical space saved. As Trizek notes, once a user opens or closes the box, that the system will remember that user's preference. Please use this space to let me know whether this idea works for you.