I think the sort of people who are looking up scientific articles would almost entirely be the same sort of people who appreciate information density and hate useless whitespace.

Your first and second points could be satisfied by showing a small PDF icon where the thumbnails currently are. Whatever size that allows the listings themselves to be as close together as possible. The PDF icon could also be different colours depending if it has a paywall, or an money symbol over it.

The really big thumbnails that mostly all look the same make the site look very amateurish on first sight.

Thanks for the feedback. The thumbnails could definitely be made smaller and/or substituted. I'll be making some sort of change but not sure exactly what yet.

Compact mode, which Reddit also offers, is an easy way to satisfy both camps. Set the default to whatever your users prefer (determine this with A/B testing) and allow the other choice in Settings.

I don't know if I agree with the thumbnail at all but if you want to keep it try to make it fit the content better, i.e. make it the same high as the right column and put the votes and the vote button closed to the content as well.

Here's an example where I on the top row changed the size of the thumbnail to 6em height and width in proportion to the page size and also aligned the votes and upvote button closer to the content. The 2nd and following entries are left with your style.

https://gist.githubusercontent.com/Hultner/e5eb15458e70eecb4...

(1) I think you should just color paywalled PDFs differently

(2) I don't think this is good enough justification for the huge amount of space wasted by the thumbnail

(3) Recognizing familiar papers isn't all that useful. Making a specific thumbnail for each sub would be better IMO.

I agree with this speaker, I would rather see an excerpt from the abstract then a thumbnail. It's much better to the distinguish paywalled content in another way, as I user I didn't get that association at all, rather add some paywall icon (maybe a warning-sign or a cross) in a colour associated with warning or danger i.e. red or yellow (think traffic lights, paywall is a stop).

1) and 3) would be better solved, I think, by appropriate text tags. And tags are also great when integrated with the site search, or even the native search/find in the browser. On some subs of reddit for example, paywalled articles are announced by a simple flair.

Perhaps there could be an option to give a pagenumber for the thumbnail when making a submission? The poster could thus optionally choose their "moneyplot" from the paper to draw attention.

Maybe you could extract pages that have figures and show one of those? Or a larger preview on hover?