Yeah, probably not. When you sign up and agreed to their ToS, they don't "own" your content, but you grant them a worldwide, royalty-free, perpetual, irrevocable, non-exclusive, transferable, and sublicensable license to use it without compensation.

From their ToS:

Any ideas, suggestions, and feedback about Reddit or our Services that you provide to us are entirely voluntary, and you agree that Reddit may use such ideas, suggestions, and feedback without compensation or obligation to you

Source: A pretty good post on r/HFY, though it is on Reddit, so don't click it if you don't want to :P