Yep, I’d also like a help vault in light mode.
Regarding the auto-resetting: I quite like it, because it allows to reproduce bugs for reporting from a clean slate.
I recommend you simply copy the help vault Obsidian comes with to another place, so you can edit it to your heart’s content.
To find where your help vault is hidden, just select Open another vault. Under Obsidian Help, you’ll see the path for your help vault (mine is at ~/.config/obsidian/Obsidian Help).
Copy the complete folder somewhere else, open it and voilà! An Obsidian Help vault with all your changes! (Light mode!) It’s only 1.1 MB in size, so the wasted space can be neglected.