Touhou Project 16.5 「Secret Sealing Nightmare Diary ～ Violet Detector」

[shockdude]

Touhou debuting on Steam was pretty hype, which gave HSiFS a really big push in of sales and reviews. In fact for HSiFS the review push was so big that the game became the #1 hidden gem on Steam for a few weeks. It helped that HSiFS was a pretty good game.
16.5 is a side game so I'm not surprised if it doesn't sell as well. Heck I wouldn't be surprised if side games were less popular than the main games in general.
Though it's also possible that there's people who, uh, previewed the game and decided not to buy it on Steam.
I do agree with Drake that it doesn't really matter whether the game sells well or is reviewed well. What matters is that people are buying VD on Steam.

[Fluury]

-snip probably just steam bugging out-

[Deftera Ikari]

This game is rather hard... I can say that it's lunatic mode on with special abilities but I can't find an English patch

[Branneg Xy]

This game is rather hard... I can say that it's lunatic mode on with special abilities but I can't find an English patch

In my humble opinion and analysis that is one of its main goals.
Touhou (and related) Photography(and Photography-like) /Danmaku genre,with "Violet Detector being indeed the " Prime among them ", does not grant the choosing of difficulty resulting in them having it " implicitly set by the genre,gameplay and mechanics".This result in a strong trend with them being milder during beginnings(tutorials),earlier stages and "even part of the first half,but  the fundamental main difficulty/challenge settings are around Normal/Hard up to Lunatic and more .Those""special abilities" are granted since the "gameplay goals and mechanic" are overall more specialized,unexpected,less known and thus are harsher,in the majority of cases,whenever considered and compared to the Regular genre  by "the standard pf sing scene and encounter" instead of "the standarda series of stages".