  Context. GitHub has introduced a new gamification element through personal
achievements, whereby badges are unlocked and displayed on developers' personal
profile pages in recognition of their development activities. Objective. In
this paper, we present an exploratory analysis using mixed methods to study the
diffusion of personal badges in GitHub, in addition to the effects and
reactions to their introduction. Method. First, we conduct an observational
study by mining longitudinal data from more than 6,000 developers and performed
correlation and regression analysis. Then, we conduct a survey and analyze over
300 GitHub community discussions on the topic of personal badges to gauge how
the community responded to the introduction of the new feature. Results. We
find that most of the developers sampled own at least a badge, but we also
observe an increasing number of users who choose to keep their profile private
and opt out of displaying badges. Besides, badges are generally poorly
correlated with developers' qualities and dispositions such as timeliness and
desire to collaborate. We also find that, except for the Starstruck badge
(reflecting the number of followers), their introduction does not have an
effect. Finally, the reaction of the community has been in general mixed, as
developers find them appealing in principle but without a clear purpose and
hardly reflecting their abilities in the current form. Conclusions. We provide
recommendations to GitHub platform designers on how to improve the current
implementation of personal badges as both a gamification mechanism and as
sources of reliable cues of ability for developers' assessment
