If mindfulness is practiced with the goal to “ignore” feelings (as stated in the text) then the negative outcomes observed are expected. However, the much better (and more “authentic”) practice is to be with the emotions, to feel them completely, and to see whether they have messages. But yeah, that might be less of a “quick fix”, as being with uncomfortable emotions can be challenging - but also more rewarding in the long term - for oneself as well as others around oneself.