Portrait of Ruin has been lacking in the moderation department for its entire history here on srcom, with SakuraFreak being the sole moderator and sometimes taking weeks to verify runs due to real-life obligations and PoR being a game that doesn't really get submissions all that often. I would have volunteered myself to mod when I started running the game, but seeing as even like Romscout wasn't modded, I assumed Sakura had things covered. Considering the timespan of your conversation, Sakura's inactivity, and your posting in the mod request thread, it seems Sakura felt he had to do something or the SRC admins would have added you anyway.

Regarding the addition of new categories, even if it's a misc category, I believe it should be: discussed publicly whether it should be added or not, a category that offers interesting gameplay that is unique from other categories on the boards, and have, at the bare minimum, 3 or more people who have either done more than one run of the category or at least have expressed interest in doing runs of it in the future(more if the game's more popular).

For example, these qualifications were all met when we were discussing whether or not to add 'Maxim, in-bounds' to CV:HoD, and what exactly the rules should be. I do not think that any one mod should have unilateral authority to add whichever category her or she wants to a leaderboard of a game with multiple runners, be it Sakura saying he would add it himself after you messaging him privately or you adding it yourself after becoming a mod. You did bring it up in the forums, but considering the only response was VB saying he doubted it would be added since it didn't have any interest, I think that was a pretty good indication that wasn't really any other interest to merit making the category.

Personally, I don't think NG+ is worth having even as a misc category in most Castlevania games, this one included. It doesn't really add any interesting gameplay to the run, and just takes away all of the difficulty of the game by letting you blaze past everything with overpowered skills and abilities. I'd much rather see something like jonathan/charlotte all bosses long before something like a NG+ category in this game. More people can discuss it either here or in the other thread if there actually is interest in adding the category(to misc at most, not main like it was before), but since I know that at least VB and myself are against it, and it hasn't garnered interest from anyone else in the past 3 months since you brought it up, it wouldn't say its chances are very likely.