The Reddit User Agreement Section 5 clearly states that you own your data:

You retain any ownership rights you have in Your Content

So you could try to use that argument to get what you want.

The agreement also continues to say you grant them a license to use this content which can not be taken away. But I would argue that if you decide to remove your content then there is nothing to license away. In other words the license is still there but the content is gone.

Of course that's just my personal interpretation. Law is a fucked up thing that doesn't follow any logic. If you're lucky your country/state might have laws that work on your favour.