As originally described in this thread and also confirmed by others, backlinks and search results always show uncollapsed be default.
When I collapse my backlinks, the expected behavior would be that after a restart of obsidian they still appear collapsed.
Yet, the actual behavior is that by default they appear uncollapsed again.
This, of course, is not a really huge problem as I can collapse them again via a click. But as there seem to be a couple of people (like me) who like their backlinks or search results in most cases only showing up with their file names, this behavior can be a bit annoying. It would thus be really great if this could be resolved in one of the next releases!