If you (and only you) analyze and review one ink* - that's an Ink Review.
If you (and only you) compare and contrast two inks* - that's a Comparison.
If you and a few of your buddies compare any number of inks* - that's a Co-Razy-Review.
Now, about that little "*" next to the word "ink" - what does that mean? We mean inks that were at some time Readily Commercially Available. This means that ANY INK that was EVER sold at MSRP before your inky thoughts.
Here's a few hypotheticals - the names have been changed to reflect the work done by one of my favorite artists and my early primers. Fun with Dick and Jane.
Here are the inks: Skrip Peacock Blue and Parker Penman Sapphire have both been out of production for decades. Both inks were sold in stores, and both can still be found on eBay.
If Jane does a review of Skrip Peacock Blue and a review of Parker Penman Sapphire, then she has 2 reviews and they both are posted in Ink Reviews. If Dick reviews the same 2 inks, then he has 2 reviews and both those reviews are added to Ink Reviews. So, Ink Reviews would have 4 new threads - 2 new reviews of Penman Saphire (one from Jane and one from Dick); and 2 new reviews of Peacock Blue (again, one each from Jane and Dick).
If Jane then does a comparison between Skrip Peackock Blue and Parker Penman Sapphire, that comparison is posted in Ink Comparisons. If Dick did a comparison of Parker Penman Sapphire and Skrip Peacock Blue, that comparison would be a new thread in Ink Comparisons. Ink Comparisons would have two threads with analysis based on the same inks.
If Dick sends Jane a letter written with Skrip Peackock Blue, and Jane writes back on the same paper and compares her writing sample of Skrip Peacock Blue with Saskia's written sample, well, that's just
Crazy a Co-Razy-View.
Outside of the bottle is any inks that are test inks, beta ink for potential inks. Then if they ever become RCA inks, the reviews that are outside the bottle stay outside, but new reviews will go in IR?