There's a confirmation pop up for CW purchases in the user shops but not regular items.
That being said absolutely no support. That would be the most annoying thing in the world when you're trying to buy more than a few items at a time and would probably cause a lot more annoyance than its worth.
No support from me. This would make buying things, especially for questing, extremely tedious. There is already a confirmation pop up for buyung CWs from user shops, which i think is good enough.
If you've accidentally bought somethibg you can always reach out to the user and ask for your sP back.

maybe only for items that cost more than 1mil (or other arbitrary amount of sP) :x ... but then that's a pretty good reason to use the sP bank (rip bank interest)

i've got to agree and say no. I think accidentally spending under 100k or so every once in a while doesn't bother me- i'd say it'd be fine to have a confirmation over 1m but my solution is just to only every keep 1m on me. if there's something i intentionally want to buy that costs a bunch i just take it out of my vault. peace of mind :)
I would rather not have any confirmations, even for things over 1mill (which in the grand scheme of things, isn't all that much). That just takes out any of fun of earning sP and going on a shopping spree. Most of the plushies I need to collect are over one million, and needing to go through confirmations to buy more than one is going to be an absolute pain.
If people are worried about accidentally spending sP, then the vault is their friend.
oh god please no this would make buying things such a hassle esp when trying to quest and that already shaves minutes off my lifespan in lag