Take a look at people who are promoted, you will find many of these have managers who speak same mother tongue (non-English).
I am not saying that the people who are promoted are d-mb, but they got tailwind in promotion because of favoritism. There are several people in Org who are equally or more deserving but they became victim of this politics.
This is difficult to detect and there is no way you can prove this as malpractice, but you can closely observe that managers groom their directs for promotions for more than a year not based on skills but based on who they are comfortable with, means who can speak with them in their mother tongue. Their favorite person gets tasks which has high visibility and others get tasks which are clerical or have no visibility.
On a worse side, these managers will not hesitate to add your name in layoff list to save their favorite person if there is a budget cut or directive to downsize org.
I am telling all this because I missed promotions due to this.
Feel free to agree or disagree with me.