Hello, and welcome to Wrong Planet.
I think it's completely acceptable to use forums like these to recruit suitable participants for your survey. As long as you are not pressuring people to participate, many members of WP will actually appreciate the opportunity to help you with your research. I think it would be wrong to use posts here for your research, and it is not necessary to do covert research when you have willing participants anyway. I suspect though, that you must already have a good understanding of the ethical issues surrounding this type of research.
The internet is a great way for aspies to communucate. We typically have difficulty understanding non-verbal communication like body language and tone of voice. Those things are not observable to anyone online, which puts us all on an even footing
Also, some of our body language or tone of voice can be unusual, and might convey the wrong message to people accustomed to typical non-verbal communication.