I have seen this in my gardens too. I usually just step on it if it is fairly small and crumble it underfoot, or break it off and put in my trug for the compost. My understanding is you will see it in places where there is high organic matter content. I do not believe it is harmful.

I ignore them.

Slime mold doesn't rot mulch and does not cause disease in plants. It eats the organisms that break down organic matter. Most of the time it's invisible to the naked eye. The orange stuff you see is the reproductive phase, when it makes spores. About the only harm it could do to a plant is smother some leaves if it travels onto them to sporulate.

I figured it wasn't a good thing to have on the stem of a plant, even if it didn't rot (eat) the plant, it would hold in moisture. It's a sign of too much moisture anyway, right?

I'll just leave it in the wood mulch.

Its not really a sign of too much moisture... it needs some moisture to grow, but so do your plants.

IME, it isn't harmful.

Slime molds may be disgusting looking but they do no harm to plants so there is no real good reason to remove them except cosmetic. They seem to appear, in my experience, in fairly fresh wood chip mulches since I've not seen any in year old mulch.

Here is a link that might be useful: Slime molds