Phoca Gallery includes a lot of parameters. Some of them are interrelated. In such case, setting one parameter does not display needed feature without setting the other one. See the relationship of some parameters:
Different Thumbnailheight --> Additional Thumbnails
Different Thumbnailheight parameter (Category view) works togehter with Additional Thumbnails parameter (Thumbnails) - if you want to display different height of thumbnails, you need to create additional thumbnails first. So Additional Thumbnails parameter needs to be enabled. Phoca Gallery will create then additional thumbnails (thumbnails with different size) to display them in Category View.
Mosaic Effect (Categories View) --> Additional Thumbnails
Mosaic Effect (Categories View) parameter (Categories view) works togehter with Additional Thumbnails parameter (Thumbnails) - if you want to display different sizes of thumbnails in Categories View, you need to create additional thumbnails first. So Additional Thumbnails parameter needs to be enabled. Phoca Gallery will create then such specific thumbnails to display them in Categories View.Display Image Comments --> Different Thubmnail Height (Category View)
If you set Display Image Comments parameter (Users) to yes and you allow that user can comment directly in Category view (below the thumbnail), it makes sense to set the parameter Different Thumbnail Height (Category View) to Yes (Masonry Effect). Normally image boxes (boxes where thumbnails are displayed) have fixed size. So if the comment will be posted, image box needs to be enlarged. This can only happen when the Masonry Effect is enabled (Every comment has different size so it is not possible to display boxes with the fixed size).