Technical people also look for "signals" or "red flags" during interview. They ask themselves questions like, if the candidate is a good fit for the team, if I want to work with him, etc.

HR people are not necessarily better in identifying these "signals". They might emphasize on "signals" that are not a big issue for technical people. Some technical people could be a little quirky. As long as it is not serious, it is not a big deal.