For me, it's that well organised forums, mailing lists, etc have some kind of metaphorically-geographical structure. On mailing lists there's also a sense of time progression as things like sub-projects and issues come up from time to time, having made progress.

Take my physical space. I have a feel for where different kinds of knowledge are based on their placement. For example in different books, on various bookshelves, on different pieces of paper, on different areas of whiteboards, even at different physical sites. Not that it is well organised (I'm messy and this is a problem for me), but when it's well organised physically that helps. For my mental map of where information is, my mind benefits from knowing where things are, and that they aren't being moved around much by someone else, without my knowledge.

Same with data on my computers, organised into directories, projects, files, even hosts. Even though it's huge, messy, and terabytes are too much, there is some kind of organisation and it's mostly metaphorically-geographical.

I don't use Discourse much. When I do, the experience feels more like swimming through amorphous knowledge. I can't really explain why, as I haven't tried to understand it; I'm just sharing my thoughts on it here as you asked for feedback.

Inevitably, I have reached Discourse via a Google search result or some link. There, I may scroll through the answers on a topic. Then I get to section at the end which shows related discussions. I read some of them because they sound interesting or relevant, and it's like walking an unstructured knowledge graph with no sense of spatial or organised structure, at least not one that fits my mind's preference for how it catalogues knowlege.

I do this graph-walking a lot on Wikipedia; it doesn't bother me that a hyperlinked graph exists. I sink hours into that some days, more than some people would say I should. I love reading Wikipedia and learning that way. It is difficult to explain why that doesn't invoke the same feeling of disorientation. Perhaps it's because the knowledge and link graph are curated models of knowledge, and that curation isn't just in Wikipedia, it's a reflection of decades or centuries of organising knowledge.

When graph-walking on Discourse, moving from topic to topic via its proposed list of related topics feels more amorphous and unstructured. More like getting lost in an sea of unknowable size. If the relevant-links are quickly exhausted for some line of enquiry I have, it's not obvious if that's because there's no more relevant knowledge to be found, or if the algorithm has deselected other relevant knowledge in favour of things that aren't relevant for me.

In this regard, it is a very similar experience to Reddit, which I also only ever land on as the result of a search, look around a little out of curiosity, and then realise I'm essentially looking at diverse, random, largely unstructured chat about barely related things, and then it feels low value.

For me I think these concrete changes might help:

- Make the list of related topics longer. I don't recall how many are shown, but it's 5 in my mind, and 5 is like being directed through the graph with blinkers on, knowing (or feeling like) there are more relevant topics to what I'm looking into that are not shown, by an "algorithm" (see Facebook). Make it 100 ("more" button), rank them well, and don't require a login for that to work, because you're not even getting a cookie until I've used the site 100 times already and want to get more involved.

- Separate the list, the way Stack Overflow does it, into a list of topics that may have related information (ideally ranked in some way, and long enough to seem reasonably complete), versus a list of interesting hot topics.

- Somehow I always remember the Discourse experience as reading a single topic, then being directed to look at related topics if I'm interested. Pretty sure it does have some topic structure, but the way I always land on discussions via search and take it from there, somehow causes me to not notice any page organisation the site maintainers have provided. I know I can look for it, but, for reasons I can't explain, my impulse is always to follow the related-topics links first unless I'm really committed to browsing more of the site. So perhaps change the visual flow, to de-emphasise disorienting graph-walking, and encourage more awareness of forum structure; and encourage site maintainers to have good forum structure.