What is a "best practice?" I normally think of it as "what everyone else is doing" whether it is necessarily the best solution to the problem at hand.
Software development requires a rich and diverse toolbox of ideas, technologies, and methodologies. Saying that "the ideal solution to problem X is to apply 'best practice' Y" is, quite honestly, a terrible idea.
The "best practice" is to use one's brain, find the proper tool for the job, and use it no matter what everyone else is doing.
"Best practice" implies there is a "best" solution to every problem. In reality, most problems tend to be complex and require tradeoffs that make each solution unique, even if just a little. In the real world, there may be two or even twelve solutions to a problem that are valid and will result in success. What is the "best" practice?
Saying that an answer or comment must adhere to a limited set of "best" practices such as SOLID is doing a disservice to the person asking the question. Yes, there are some good software engineering principles that are broadly applicable, but not universally applicable. SOLID is not always the answer: in fact, for some problems (rarely), it is a bad thing.
Solutions are not one-size-fits-all. One of the marks of a good software designer is knowing when to take all the SOLIDs and DRYs and throw them out the window in favor of a solution that is not over-engineered. Yes, I have copy and pasted code. Yes, I have violated the Law of Demeter and Liskov Substitution Principle. I try to adhere to those principles when I can (99% of the time), but sometimes, they are not the "best" solution to a problem.
Finally, as Thomas said, this site is community moderated. You have high enough reputation right now to do your part to address the shortcomings you mentioned. Once you get to the point you can downvote, the next major milestones (in my opinion) are 3k to cast close votes, and 10k to cast delete votes on questions. However, your issue seems to be with answers and comments, which you are already empowered to do something about.