TLDR: Double Counter stores a bunch of semi personally identifiable information for the purpose of identifying you and your alt accounts!! be careful!!
Double Counter is a discord bot that detects alt accounts through a variety of techniques, including IP and browser fingerprinting, and probably others which I don't know of.
if your account is flagged, the information (with you and your suspected alt) is sent to the server moderators. they also have a paid service that you can subscribe to in order to search their database of discord profiles for alts.
the paid service is opt-out-able, using a command, but the command is not available in DMs so you will have to use it in a server with Double Counter in it, and some server channels don't allow it.
data deletion is only partially (it's only stated that they will delete your IP) and locked in their server, behind a 10 minute wait.
I just requested a copy of my data (which is sent by email, you have to fill in an email) but it hasn't arrived yet - apparently right now that system is down
anyways this whole thing screams red flags to me & if you get a message from it telling you to verify, use caution!!!! you have to click a link to get to the verify page, that's how it collects your information.