kalmdown

It's like that. With the problem described AndyQ seems to back our feelings/impressions perfectly: after some time anybody working in pixel graphics will have realized that pixel masks ARE in fact just grayscale images applied in certain way to select corresponding pixels (meaning those having the same 2D position on the canvas) and allow to do certain things to them (i.e. adjusting their opacity etc.).
This given it seems only natural that masks should be editable just like any other grayscale image (including copying, pasting, painting in it, filtering it etc.) once you have them as the contents of your active window.
In Photoshop this is very much the case once you know how to make the mask content visible as the actual content of your active window. It doesn't take more than just going to the channels panel and clicking on the mask's channel – there you go and it's easy and intuitive. And turning the mask's content to a selection which you then can use in any pixel layer, adjustment layer, channel or other mask of your file is just one more click away...
In Affinity Photo this whole "field" of channels masks, selections and pixel layers is generally organized in such a "fragmented" approach that it becomes ”cryptic" as no obvious logic becomes apparent: so it becomes hard to understand and cumbersome to use. In effect you experience exactly what AndyQ said: you spend a day on a job which you could have finished in an hour with Photoshop. And true: as the way of achieving comparatively simple thing is so unnecessary complicated you're prone to have forgotten at least half of it of it by the time you have to work on the next job needing this a month later.
Please, to all you developers at Serif: I guess there are quite a number of guys here among us who REALLY WANT to work with your apps, who REALLY WANT you to succeed long term on the market. The workflow must become smoother, more unified and necessary actions for closely related goals should not be scattered over different places in the UI. I'd think in the end it just has to be at least as efficient as it is with those applications you – rightly – chose to challenge. Let's be honest: there may actually be a limit to the time professional users can afford to spend with Affinity Photo or Designer on jobs they could have finished in a fraction of the time needed if they had just reverted– however much loathingly – to Photoshop and Illustrator.

Hi @kalmdown,
Thanks for your report & file provided!
I can confirm I'm able to replicate the selection inconsistencies here, so I am logging this file as a bug with our developers now.
I hope this helps

... as usual, where it is not clear to me whether you are only re-describing an obvious symptom, a known, already stated issue or missing option multiple times – or whether you are trying to provide an explanation as to why a particular process discussed never would be able to work in general.
A node dragging (or node existence) is generally irrelevant / no condition for snapping – it is rather that Affinity "just" does not offer the according interface. Thus, it could snap with the Move Tool for each single key point of a parametric object, without having to convert it to curves or explicitly grab that point – regardless of this point's visualisation in the UI.
Also, Affinity could snap to any node of a Curve object, not just the node currently grabbed and used for dragging the object with the Node Tool.

Illustrator can do it.

Because their functionality is being constrained/dictated by the shape tool protocols. They become individually (or more) editable upon baking, i.e. convert to curves.
This is by design by Affinity. It doesn't have to be this way.

To draw a selection around nodes, select the Node Tool and hold the Option Key down while you move the cursor around, it may be a different key on Windows.
Hint bar on Mac


Polygon select

Welcome to the forums @kalmdown
If you have a Curve Layer selected and are using the Node Tool, you can use menu “Select → Select All” to select all of the nodes in that curve.
Or, if you have a Curves (plural, not Curve) Layer, and want to select all of the nodes of a particular curve then you can select one point of a curve with the Node Tool and then use menu “Select → Select All” as above.