I noted that after installing this plugin I lost my magic comments highlights, as you can see in the following picture:

On the left you have the editor without vim-yardoc plugin, on the right the same config with vim-yardoc plugin.
Code for Magic Comments is here:
https://github.com/vim-ruby/vim-ruby/blob/master/syntax/ruby.vim#L433-L434
I noted that after installing this plugin I lost my magic comments highlights, as you can see in the following picture:
On the left you have the editor without vim-yardoc plugin, on the right the same config with vim-yardoc plugin.
Code for Magic Comments is here:
https://github.com/vim-ruby/vim-ruby/blob/master/syntax/ruby.vim#L433-L434