Yes I would, because the boundaries of the artboard clip it, so it doesn't cause problems. The purpose is that I don't need to set up a mask to trim the object/symbol, and can easily reposition it if needed.
Also, if the stroke (1px solid black border) is added to a rectangle at the bottom of the stack, even if I trim the object with a mask so that it doesn't extend past the edges of the artboard it will still obscure the 1px border, like in the examples I attached earlier.
I could spend time fiddling with the masks so the border isn't obscured, but it would take more time than I want to spend on this single problem, and I would have to do it to any element that went right up to – or past – the border. It's especially frustrating when I know the one-step solution is supposed to be possible – adding a stroke to the artboard – it just still isn't working a year after it was added to the development queue; unless I use your tip of adding another stroke through the Appearance panel, I'm very happy that's working.
By design and according to the help file, a stroke on the artboard is above everything contained on the artboard.
From the help file (https://affinity.help/designer/en-US.lproj/index.html?page=pages/SymbolsAssets/symbols.html?title=Symbols):
If a color is applied to the artboard's stroke, it will appear over any objects placed on the artboard—therefore acting as an overlay.
To take full advantage of an artboard's stroke appearing in front of artboard content, you may wish to set the line to Align Stroke to Inside on the Stroke panel.
You can see from the template file that I've made and attached how it works. When you go to the Export Persona and export the 160x600 and 300x250 ad sizes, the resulting png files have the background clipped, and the 1px black border is where it needs to be. My first version of this template was so convoluted with groups in order to get the border to work that it was a pain to deal with, and cluttered. With the strokes on the artboards, this one is much easier.
I'm still learning my way around Affinity's products after 20+ years of designing in Photoshop, Illustrator, and InDesign, and I keep having to puzzle out how to do things that had become second nature for me with Adobe's products. This is one of them. But there are so many good things Affinity Designer is bringing to my workflow that I feel like the time and frustration will pay off eventually.
Thank you again for your tip though. It's working perfectly.