Reason: While not an easy-to-write name, it's the name he uses everywhere except his stacc name. For the second one, I don't know where "yato" came from, but "pondel" (or "pomdel") is the name he uses everywhere since the beginning. As for the last one, "sakuya" is his current name, with "liao_kj" as his Twitter handle.
Reason: Using artist's name instead of stacc name (with 10011 from his Twitter handle for the first one). For the last mass update, artist's Twitter handle where the name came from was deleted, and he is known as "Subaru" from the beginning. And for the last one, artist's name instead of Twitter handle.