Broken Base: Name exclusivity (in other words, someone's dragon cannot have a name if any other dragon on the entire website has that name). A long ongoing thread suggesting its removal sparked some very, very vocal opinions; the side wanting the feature gone advocates that name exclusivity breeds frustration by severely limiting what someone can name their dragons (common names, for instance, have mostly been long ago claimed) and thus stopping people from naming their dragons what they want, and the side against the feature's removal argues that name exclusivity makes each dragon unique and encourages creativity when naming them. The disagreement even ended up becoming so bad at one point that users began attacking each other, leading to moderators getting involved.
Fan Nickname: Every breed has one (or more) official names, though a handful are popularly known as something else, e.g. "Vine" for Dark Green. Holiday Dragon (2007) is near universally called "Holly Dragon" by players, although the dev has stated that its name was meant to be Noel Dragon. In a case of Ascended Fan Nickname, when "Two-Headed Dragon" was renamed, it took the name "Split Dragon", since that's what numerous players were calling it.
Scrappy Mechanic: Dragon sickness. While built for the purpose of requiring players to actually "take care" of their eggs and growing dragons instead of dumping them on a hatchery site and forgetting about them for a week, the way it's implemented is very much prone to abuse - it's possible for a malicious user (typically called a "viewbomber") to put another user's eggs and hatchlings into as many hatchery sites as possible, making those eggs and hatchlings rack up so many views that they get sick and die, which is especially painful if said eggs and/or hatchlings were one of the rare species such as Gold Dragons. As a matter of fact, it even led to Eggs Around The World, one of the most popular hatchery sites, to shut down after a paid-for attack which involved launching over a thousand bots that incessantly gave views to the point of killing growing things in as little as thirty minutes after being put into the site.
. In a case of Ascended Fan Nickname, when "Two-Headed Dragon" was renamed, it took the name "Split Dragon", since that's what numerous players were calling it.