Well from what I gathered it’s when you start translating a manga that another group has already started.
It’s bad because then the ones who started first and were putting time and effort into good translations loose viewers to the ones that perhaps are doing it faster so are deemed ‘better’.
But basically it’s not polite and since there are generally tones of untranslated projects or even dropped projects, they could go and do something else
Who is the male lead?
according to novel spoilers, it's Daejun!