Max, bugs aside, one thing we have been discussing in depth ever since the last wave of new sub-genres were added is how the site may develop even further. Speed and groove metal are both growing well, but having discussed it (and getting collab input) the admin team is in agreement that we should expand further in order to accurately cover all the different sounds of metal. 

This information is in the AZ also, but these are the expansions we've agreed that we'd like to see added.

Main sub-genres:

Stoner Metal

Drone Metal

Both of which are currently inclusive with doom metal, which isn't completely accurate. The situation is similar to how speed and groove were given their own sub-genres instead of being in with thrash metal. These two are the priority expansions.

These next ones are child sub-genres. I'm not sure if you ever considered expanding the site in this way before but we've spent almost a year gathering feedback from the collabs and there is support to go into more detail for certain sub-genres rather than simply tagging artists as black metal or death metal for example, both of which are very diverse genres. Obviously to get these right it's going to be a lot of work, but my view is its better to start such a job early (which is why for black metal I've been marking the specific BM style for every artist added or updated for some time now).