Earlier quoted context omitted.
I'm not disagreeing with you, but I have worked with world-class scientists where the author only had a gmail address (untill we gave them an appointment at Berkeley).
Of course, a gmail address in and of itself is not an indicator of quality, however on a single author paper it certainly makes me wary. Just out of curiosity, what field was that in? I could certainly see some scientific disciplines having unaffiliated world-class scientists, but others it would be virtually impossible to do high quality research outside of a lab
There were already a few codes in the area and plenty of papers, and he was mathematically inclined, so it didn't take long for him to become an expert. Once he was an expert, he pointed out major problems in existing codes (both functional and performance).
This is an area where you're working with fairly straightforward data and math (linear strings from a chosen alphabet, probabilistic model is well-established). You don't need to understand the underlying biology in detail to contribute.