Enforcing rules is important

Stackexchange websites are good at two things: Providing answers to good questions, and creating an archive of such answers. SE best practices have been honed to do these two things. It is much easier to create a culture of sticking to the best practices when the site is young. Changing the site culture afterwards into better shape is painful and might not work. In particular, the best practices are vital for creating a functional Q&A site, so there might not be any future if the site does not stick to the best practices.

The best practices are for using the website as Q&A site, not a discussion forum, and for making it work as a proper archive of information.

I could be nicer about it

My comments were curt (not hostile), but it is easy to read hostility into curt comments. I take this thread as a feedback to that direction. More concrete suggestion would also be appreciated.

Partial answers in comments

I quote a meta thread at RPG for the reasons why partial answers in comments are a bad idea:

You should not answer in comments. Not partial answers, not full answers. Not "leads on" an answer. Not "I would answer but I'm tired/just woke up/am drunk so I'll just say this..." These will be deleted. Answer in answers.

Answering in comments does the following things.

1. It bypasses question closes. They're closed for a reason.
2. It provides an answer that can't be marked as an answer for future people's knowledge.
3. It contributes to long comment debates as you can comment on an answer, but it's unclear what you're commenting on in a comment thread.
4. It is "cheating" by locking your answer to the top. Answers with higher votes/accepted answers should go to the top to indicate their quality. Bypassing that by sticking your answer in a comment on the question is unacceptable.
5. It bypasses all our quality control mechanisms: we can't downvote your "answer", edit it, or comment on it to request clarification or improvements. Answers also bump a question to the top so that people will scrutinize the answer; comments don't do this.

The long and short of it is, every part of how how the site functions, all of which have lengthy justification as being part of the process of SE - rep, answers, accepts, edits, etc - is obviated by using comments for answers. So every good goal of all that functionality is nullified by this practice.

Now, "but the hapless questioner could use that info!" In nearly all cases someone posts the same information in a (much more comprehensive) answer. Or take the time yourself to write a real answer. We don't like crappy questions or crappy answers, and we'd rather not have the Q or A than to have one that doesn't meet site quality (hence closes/deletes, part of the standard SE functionality). If you don't care enough to write a real answer don't, the likelihood that you're the only person in the world/on the site that knows that bit of info is very small.

While users are welcome to steal the info in the comments to generate answers of their own, that will not slow the pace of dealing with the answers-in-comments via flagging and deletion.

This works quite well at RPG.

I also follow, and occasionally try to use, various mathematics StackExchange sites. They contain plenty of questions that only have incomplete answers or hints in the comment section, and no proper answer. People also have a tendency of answer in comments, often in a non-useful way. This greatly reduces my inclination to use those sites. I could answer a question now and then, but since the comments already have much of that, why bother?

Incomplete answers

Answers to questions should stand by themselves. An incomplete answer could raise to the top, or the other answer could be deleted, which would significantly reduce the value of the incomplete answer. Further, readers should not have to read through several answers (and perhaps their comments) to find all the information they can have.

If one wants to add to an answer, they should suggest the addition in a comment. The answerer might or might not choose to incorporate it. It is also possible to try to edit it in, but many find this impolite, so I would not in general recommend it. (Though feel free to edit my answers to add content.) The other options are writing a complete answer which includes the information in the other answer, usually reworded and with possible attribution. Having a community wiki answer might be appropriate, if one for whatever reasons feels bad about earning reputation by doing the work of combining answers that others have not bothered to do.

Website development

The site grows by having and providing good answers to questions. This is done by writing complete answers and by not making comment answers, which easily lead to situations where have to fish for the relevant information by reading long comment threads. These bad habits will make readers not find the website useful, and so will not attract them as users.