It was questions like that one that I had in mind when I first made the proposal.
My answer to your question during Area51 alluded to the fact that VASP, MOLCAS, CFOUR, GAUSSIAN, LAMMPS, CP2K, DIRAC, Turbomole, MOLPRO, ORCA, MRCC, ADF, PySCF, PSI4, DALTON, QuantumEspresso, QChem, CASTEP, CPMD, ABINT, DFTB+, ABAQUS, OpenBabel, may all have their own individual forums or Q/A sites.
Rather than giving my email address and making a password for each and every forum, it would be nice to have one unified place where people can ask a question with a "tag" that reaches the desired audience, and have it potentially seen by 30x the number of people.
Area51 was not an easy process to get through, and people wondered why myself and Rashid, and Cody, and others worked so hard at it: it's because we believe in Stack Exchange. Questions and answers are available for anyone online to benefit from, so that they don't have to bang their head against the wall for the same problem that someone else already solved. The search function is excellent. The automated search for similar questions, helps askers to avoid asking a question that was already asked. The upvoting helps reward users for providing high-quality answers, and motivates (some) people to put real effort into their questions.
To register for the VASP forum, you need to be given a registration code, which is only given to people that have paid the $6000 fee to keep their license valid. So where do I go if I (not yet a VASP user, but interested in whether or not VASP might be able to solve my problems) want to ask a question about VASP? That aforementioned Area51 answer shows that there's 1000+ VASP questions on ResearchGate and 2 questions/week on the VASP facebook group (back then, much more now). However, primarily VASP users follow those groups. The answer you are really looking for, might only come from a PySCF user, because VASP users will be very unlikely to know about the brand new cutting edge features of PySCF such as coupled-cluster for solid-state materials with periodic boundary conditions using plane-wave basis sets (a rather new area, since until recently coupled-cluster was way too expensive to do on solid state materials). But how does the user know that the PySCF forum is the right place to ask? It would be impossible to expect them to know which of the 200 software communities to reach out to.
However we have built a community here with major representatives that are lead developers or major developers from many of the most important software packages, committed during Area51, here's their Area51 profiles:
Many of them were unfamiliar with Area51, and a little bit put off by the UFOs and aliens and overall "look and feel" of Area51 (which I admit has been that way for about a decade), so they sent me emails asking to clarify about the confusion. I told them to hang tight, and the only reason we don't yet see some of them here is because I don't have confirmation yet about our chances of being approved for Public Beta. When we do, we will have these lead software developers come roaring back and in many cases a big community of followers will come with them.