How complicated would it be to exclude original posters from being able to answer their own questions?
Browsing through the ask.LO site, this problem is almost as common as the wiki-question thing. Just the amount of work I see going into asking people not to use an answer, but to make a comment instead, is overwhelming.
Is there any reason for an OP to be able to answer their question, other than by making a comment?
Sometimes (well, quite rarely) they really answer their own questions.
I fully agree and personally I feel pretty uncomfortable to tell people ever and ever again, that there are other rules or to explain that this is a Q&A site and not a forum. From OPs view there might emerge some discomfort about these “nerdy wisenheimers telling me how to communicate instead of answering my question”. As long as this site is as it is, I’d vote that OPs should not be able to answer their own question. I’ve got no numbers, but my gut feeling tells me, that more than 90% making the “answer instead-of-comment-error” do not belong to the category of people investing time to solve their own problem(s) and rightfully answer their own question.
The only idea I could imagine which eventually could be implemented quickly, because it might fit into existing implementation and fuctionality, is to require a certain karma level to allow for answering own questions.
Was just wondering; If OP can’t answer his own question, he could comment on it and mark the question [solved] - wouldn’t that cower most use-cases?
When OP finds on his own the answer or a workaround to his question, it is beneficial to the community to know the answer. Also, it shows “frequent contributors” (what about a club membership card and reward programme 
?) that OP has taken the pain to investigate, search and study. OP has not waited passively for a pre-cooked solution.
There are also questions turned into tutorials by experts: a question, thought to be representative of a widely shared problem, is asked with the answer immediately written to serve as a step-by-step guide. Usually, such “tutorials” are rather related to AskLO site, see the Guidelines for asking as an example.
The problem is rather the poor ergonomy of the AskBot framework. It seems there is no way to have a “permanent section” where the rules could be better explained than in the present situation. This permanent section could also hold several recurring questions with comprehensive and definitive answers.
The biggest difficulty with newcomers (I remember how I was scowled in the beginning) is to understand the difference between a Q&A (question and answers) site and a forum. A forum is a sequential chronological conversation which progressively converges toward success or failure. In Q&A, the question is unique but editable to be accurate, precise, detailed and informative. Each contributor is then allowed a single answer which is also editable for improvement.
Comments are there to request additional details and, theoretically, should be considered as temporary and expendable: their important information should be transferred either in the question or the answer.
As for your question: yes, OP should be allowed to answer his own question but he must be made aware of the rules. This is the real issue.
If I may…
@ajlittoz, with all due respect, your “answer” is unarguably correct…but totally unrealistic. A major part of the people asking questions are new users. They already are looking for answers about unfamiliar software on a site which is perceived as a forum-type site, a large part of them never to return anyway. In fact, I was thinking as I read your “answer”…it isn’t an answer! It’s a comment! XD That said, although I agree in theory that a questioner should be able to answer his/her own question, due to the incredibly high number of comments-as-answers, I’m in practical agreement with @sveinki 's last comment (2019-04-12, 12:02).
…but what do I know?
@gtomorrow: you’re right, I broke the rule. My “answer” is part of the debate, just like we’d discuss an idea on a forum. But comments have a limit presently set at 1000 characters which is short in some circumstances (it used to be shorter not so long ago).
Yes, most new users are one-shot users, never coming back again, looking for a pre-cooked answer rather than taking time to read the manual beforehand or even going to the built-in help. They are used to other applications and don’t understand (or worse don’t want to understand) why LO is not the same as their previous application. However, there are plenty of Q&A sites, like StackOverfolw family, AskUbuntu et al. The Q&A concept should be familiar, even if not mastered.
Note: OP (and only (s)he) can repost answer as comment (the “more” menu at right below answer); This could be done by OP after a reminder remark.
The solution might be @anon73440385’s suggestion: requiring karma points for self-answer.