What serious issues are being created? I'd like to hear this.
You people need to chill out. No gil is being generated here. All of it is simply changing hands. Supply -> Demand. Someone has something other people want to buy with gil, so they buy it. No "RMT" is happening here and it sounds like associating the term with this is causing the devs to misunderstand exactly what is happening.
If anything, you know what this really means? Something in the cash shop is attainable in-game for enough gil. How is that a bad thing? I thought you people wanted that.
I interpreted the dev response as "Well, we didn't expect people to start selling it. That's interesting. We need to look into whether this is good or bad before we act. If it IS bad, please stop propogating the problem until our fix."