Personally, I wouldn't be thrilled to purchase a board and find sticky funky tape stuck to it. There's no reason anything would need to be covered in tape.

What would that do? Insulate that one spot from a short; verses the hundreds of pins already there? A properly mounted board shouldn't have any problem staying away from things shorting it.

If it doesn't have any corrosion, you could do a couple options, that I could think of. Just leave it, since it's tinned. Or some people may say put a clear of some type over it.

Personally, If I was worried about it, then I'd probably get a little tube of green solder mask and touch up the board. But in all reality, as long as it wasn't corroded, I myself would probably just leave it be.

I believe the solder mask on those types is to primarily help protect against oxidation of the board, as the copper traces under the mask have already been tinned over, from the wave solder, during manufacturing. It is not bare copper under that part of the mask (as you can see). At least for that section.

But yes, solder mask layers are also used to help other traces and things from having solder bridges get across traces, pads, vias, etc. of course.

And obviously top, confomal coats aren't something we would typically see in pinball. So no need to go into that.

If it was bare copper, I may have had more concern to seal it. But since it is a section that is tinned already, I agree that it shouldn't really be a concern, as it is.

Noticing corrosion or oxidation would be a different story, obviously. But that board looks clean to me; from what I can see.