I think we (= users) are expected to mainly use this site (Discourse) or Gitter for asking questions or any topics (in addition to StackOverflow), and it seems that Gitter is most actively used. However, as far as I experienced, Gitter is not very easy (if not impossible?) to find topics of one's interest, because conversations just start without any title / category (so I need to read each post to understand the content of a question), and also posts are sometimes mixed among different people (though we can read replies at once in a sub-panel). Because of this, I feel like Discourse would be probably better for this purpose, particularly for search capability of desired topics. So I wonder if there were previous discussion(s) about the pros/cons of Discourse versus Gitter somewhere...? If there are such pages, I would like to read them to understand previous discussions / opinions of other people.
(In the above comparison, I excluded the (official) Github issues site, because my understanding is that it is not very much suited for user questions (but more suited for reporting real issues like possible bugs in build tools and the compiler).)
I think your characterization of the situation is fairly accurate. I think of Gitter as being a fairly unstructured and lightweight platform, though also a bit like a stream of information that isn't particularly easy to review beyond what's currently going on, due to its lack of structure and subject titles, the chatty nature of it, etc. I don't fault anyone for using it because I think it's easy to get started with, particularly if you have a GitHub account, and it provides a virtually real-time interaction (similar to texting) when people happen to be online and paying attention to it.
In contrast, for any conversation that requires more information, longer responses, better formatting, or would benefit from being archived or having a title, etc., I think Discourse is the best choice for the reasons you mention. Since it can also generate emails in peoples' inboxes (for those who subscribe to categories as though they were mailing lists), it also "pushes" discussions into peoples' lives a bit more than Gitter does, while still permitting them to opt out of a given discussion or category that they're not interested in. So that could be another reason that people use Gitter for simple questions—if a user didn't feel like their question was worth an interrupt in others' inboxes, they might reach for Gitter, feeling like it's less intrusive (?). Not that I think anyone should obsess about this—there are ways to filter or distill what Discourse sends via mail.
Offhand, I'm not aware of an existing discussion (within our community) about the tradeoffs of the various approaches beyond the very short descriptions we have on our Chapel: Community page.
Since you mention them briefly, I'll add that I think your assessment of GitHub issues is correct—we think of that more as a place to file issues or action items than to have general conversations or ask questions. I do want to say that I think Stack Overflow is a great place to ask questions (or even answer them oneself), since it's such a popular and technology-neutral place to build up such repositories of information. Of course, it's best for cases that have a self-contained question that can be answered rather than having an ongoing conversation. I also think it'd be great to have more questions showing up there over time for that reason (or to distill questions out of longer conversations into SO Q&As to capture the information).
Thank you very much for detailed information! Because I haven't used Gitter for some time (and the interface have changed somewhat), I wondered if there were discussions about where to use as a "main" forum. I agree that Gitter is more lightweight and so maybe easier to post a quick question. But one concern is about search capability via general search engines. For example, if I click the Room Info button at the top-right corner of Gitter and then click Search button to enter some search word (e.g., "array dimension"), it simply gives an error with the message
Search failed
MatrixError: [403] Guest access not allowed (https://gitter.ems.host/_matrix/client/v3/search)
(here, I tried to use it as an anonymous user.) If a similar limitation possibly applies to general search engines, I am afraid this might significantly limit the availability of various info and coding TIPS. Also, if I google with keywords like "xxx array dimension" (where xxx is the name of a language, e.g., xxx = Rust), it shows some results of their Discourse site. If I set xxx = Chapel, I get pages from this Discourse site (in addition to StackOverflow and Github issues), but not from Gitter. So I suspect the information in Gitter is possibly hidden behind the registration wall...?
So, although I believe it is just one's preference which forum to use, I was a bit afraid that Gitter might be unfavorable (?) in terms of internet search engines, in addition to search / bookmark capability etc.
Just to report something I noticed recently
-- Takeshi
I have to admit that I'm not that familiar with Gitter's integration (or lack thereof) with search engines. At one point we were actively considering moving from Gitter to Slack (now it's more of just a passive idea), and one of the considerations raised by @daniel.fedorin at that time was that Gitter had better integration with Google search results than Slack.
But I think that characterization was before Gitter migrated to Matrix, so things could've changed since then (?).
If there's something we haven't configured properly to permit search engines to index the Gitter channel, I think we'd want to change that; but quickly scanning the settings on the channel, I'm not seeing anything suggesting it's anything other than open at present.
Thanks very much for checking the Gitter configuration. Because I know almost nothing about the mechanism of search engines, I will try to check statistics of search hits from time to time and I will report back here if I notice something.
I will also try making such Q/A on SO when I find useful conversations / info here on Discourse or Gitter. By the way, I personally feel Discourse is much easier to ask questions (in general) than StackOverflow. The reason is not so clear, but might be because Discourse allows an open discussion (and it also allows questions about "resources" (IIRC, SO does not allow some kind of questions like that...))
This hints at an unfortunate aspect of the migration of Gitter to Matrix. Prior to Matrix, all Gitter conversations were indexable by search engines (you could google for a message that was sent to a channel, and would find a link directly to a gitter log at that position). However, I think that Matrix has no support for this whatsoever, so I think Takeshi is right about the search engine difficulty of Gitter.
As a consequence, today, Discourse is definitely significantly better for finding old conversations.
