Cavalary: Don't know if this was mentioned before, but noticed that if I select to just see improved discounts the list doesn't include titles where only DLC discounts are improved while the base game isn't unless I turn grouped view off.
Yeah, all filters only apply to the main game in grouped view (other than for those in the "Has a grouped product" section). Things'd get pretty weird with the price and discount filters otherwise, and I figure consistency in behaviour is worth more than the use of making discount quality an exception.
This one annoys me too, though, so I've been thinking about adding two filters
just for discount quality: improved / improved (year) for main games + grouped products. Sorting then becomes an issue (is that filter still useful if the non-improved main product with improved grouped products sorts below everything else), as do interactions with other filters (what if I'm also filtering by wishlist, and the improved grouped product isn't on my wishlist?) And the easy solution is just to toggle off grouping, so I'm keeping things as-is until I find a satisfactory solution to all of that.
Cavalary: Also see that if grouped view's on, to see the GS page for a DLC you need to first go to the page for the base game and then select it from the list from the bottom of that page.
Granted, when the main link goes to GOG, don't really see how else it could be done.
When you have JavaScript enabled, there's actually a tiny graph icon for each grouped product (after the price information), which links to the GameSieve game page for that product. I'm not putting that into the HTML out of a misguided attempt to reduce the immediate number of links most AI-scrapers see by half, and keep the page size somewhat limited. (I find the JS requirement acceptable here since otherwise it's only a single extra click to get there from the main page.)