This looks like a really nice improvement @Julian Eisel (Severin). I know I struggled a lot to always get it to splice how I wanted.

I'm not so sure about choosing the noodle with the most intersections, though. This seems like a very strange criteria to me. My first thought was that it should resolve conflicts by the noodle nearest the mouse cursor.

@Jonathan Williamson (carter2422), Using cursor position wouldn't work, keep in mind that the cursor can be at a completely different point than the node.
Simple scenario where this wouldn't work: Imagine two links, one higher than the other. If the cursor is placed a bit higher than the moved node, the upper link line will always be active. If you wanted to activate the lower link line, you had to move the mouse cursor close to the lower line but this again would mean the node is moved downwards, probably so far that it doesn't intersect with the link line anymore. Result would be that you couldn't select the lower link line at all.
Only using one axis for this wouldn't work either afaics.

So to avoid such scenarios, the method needs to be based on the node position.

Using the link with the most intersections just was the method that worked best for me, I tried many others (distance from node center, distance from node header, old method, first/last created link, ...).

I'm impressed. This works SO much better than the old behavior!

Tried the latest changes and it still is amazing. Probably even more. It is no problem to insert new nodes into even the most narrow, crowded, crammed spaghetti nodes. :)

The only open question I see here is which point we should use for measuring distance.
E.g. upper-left corner (as currently in this patch), upper-middle-of-header, node center (seems logical, but node link might be completely overlapped by node, making it hard/impossible to see)

This is something that should be tested by and discussed with users, so feedback/testing welcome!

In D1393#30218, @Julian Eisel (Severin) wrote:

The only open question I see here is which point we should use for measuring distance.
E.g. upper-left corner (as currently in this patch), upper-middle-of-header, node center (seems logical, but node link might be completely overlapped by node, making it hard/impossible to see)

This is something that should be tested by and discussed with users, so feedback/testing welcome!

I find the upper left corner to work precise, reliable and indeed better than the center in cases of narrow and crowded node arrangements. I was going to ask why not to use the right corner, but because nodes collapse from right to left when hidden ("H") I suppose upper left is the best solution.
+1 from me!
:)

Upper left corner seems very intuitive for me. For some reason I automatically try to 'cram in nodes' with their upper left corner, collapsed or open. So also +1 from me!

+1 top left. It's definitely much more intuitive and allows sneaking nodes in the smallest places, this combined with auto-offset makes node editing a dream!

Thank you so much for looking into these usability issues, they're gold.

For me too it's seems a lot more natural to detect it on 1 side (and not on the center of this side).
The upper left corner is a good choice, for the same reasons as @Sebastian Koenig (sebastian_k) and @Jasper van Nieuwenhuizen (jasperge).
Another +1 :)
And thank you for you work :)

Committed rB4041e654cd145cc0, thanks all for the feedback! :)