Where do general researchers make general discussions, online? I am involved in a project team to build a decentralized tool for researchers to share and peer-evaluate their findings, without any intervention of third party intermediaries (publishers, journals, presses, ...).

The team aims to work as a non-profit foundation, and the service (or the platform) of course is gonna be open-sourced free software. The problem is, in building the designs and specifications of the tool, we need opinions from the academics.

So here is the question. Where on the Internet can I find active discussions and opinions from researchers?
(I've been told often that many researchers use Twitter, but if that is the case how may I reach them? Does it work like hashtagging #ScholComm, #SciComm, or #Researcher?)

PS. for those who're interested in what the project is, please message me... or am I permitted to link it here?
A lot of them are indeed on Twitter, but as usual with humans, cold asking them is probably not appreciated by many. What you can do, though, is simply follow them and see what they're saying, as they're saying a lot. You can find the people you might want to follow through hashtags indeed - the ones probably most open to your ideas will be talking about #OpenAccess (or #OA), #OpenScience, #ScholComm, #ICanHazPdf, off the top of my head.

Something that might work better is addressing them in real life. I'm told they mostly hang around universities, so you might try and approach people there to ask whether you can have five minutes of their time.

PS. I don't think there's a way of messaging on Stack Exchange, but if you make a Twitter account and share your username I'd like to contact you.