So I have a P0420 and it may be a bad CAT. I have read very different info about this online and also have gotten different info from Honda dealers. Some have told me that other than state inspections which I don't have to deal with and possible poor mileage that a bad CAT won't cause any harm to the car.

Another Honda dealer and several replies online mention that a bad CAT can cause engine damage or other damage to the car. Which is correct?

Its a pretty expensive repair so if its not going to cause me any damage to my car I'd rather wait on getting it done. Any thoughts on this?

if its clogged, it can cause damage.

as Gearbox said, if it is clogged, It's like your A$$ is clogged and you can't put what's inside to go out. Would it damage you?
Anyway, check if it is not clogged, if not you will just fail emissions...
Easy...

Well said lol. Is it easy for a tech to check the CAT to see if it is clogged or does it need to be removed, etc. If it is not currently clogged, can it become clogged easily and is there really any way for me to know. I will get it replaced at some point in the near future but have some more important and immediate repairs that need to get done first.

cant you find a used one off ebay? from a younger car maybe. idk, its a pretty important thing to fix.