@liu
It's when a translation team is translating a comic, then another team swoops in and translates ahead of the first translation team. Then, it usually devolves into either translation team loyalty, or reading whoever releases first. Usually, people just read whoever translates first, unless its a troll translation team or a bad translation team like in the case of SSSS. The unwritten code is that if a translation team is currently translating a comic, they're the sole translators for some given time, and as long as they release translations on a regular basis and the quality is good, "polite" thing to do is to either wait a few months to see if the current TL doesn't translate anymore, or ask them properly, though it is sometimes against translation groups that sit on too many comics at once and are unable to release translations in a timely manner, like LHtranstions with some of the titles it hoards.
At least that's how I understand it.