Since JRuby 9.1.3.0 yard stopped working. More precisely it is probably not able to align comments with actual elements. Same project, same version of yard, "documented" dropped from 100% to 28.57%. Also it started to print warning "Unknown tag @host", however there is no such tag in comments and this warning is generated based on commented instance variable within method implementation (therefore I guess there is some problem with comment alignment).
Everything is working as expected in JRuby 9.1.2.0 and older (including 1.7.x)