How does one thin honey?

Try to heat in Microwave for a few second. Pure honey does not crystallized usually.

One does not simply thin honey

Heat a pan of water to a simmer. Turn off the flame and let the water cool somewhat so that it does not melt the bottle (if plastic) and then put the bottle, tightly closed in the hot water higher than the level of honey in the bottle.

First attempt - Dry heat in the nuke.

Second attempt - Wet heat in a pan with some water.

Third attempt - Dilute by adding a little water.

If it is in a jar remove the lid and microwave a few seconds at a time stirring frequently - once it is hot enough it will clear and de-crystallize.

Heat it. It's fine in the microwave for 10 seconds.

I've (carefully) used the microwave to loosen up honey.

Yes you can put it in a microwave. Few Seconds only.

Fill a bowl or sink with hot water, put the jar in that for a while

warm it gently and yes you can put it in the microwave for a few seconds at a time or simply set the jar into warm water.