A post can be well constructed and quality of about 500 characters, but if the purpose does not fit, it is a spam.
If you can say something shortly, making the post longer makes it a shitpost. Making it longer is actually worse, because it takes the reader more time to realize he should ignore the user.
My stance:
If you can post a constructive post in 12 words, you don't need to make it longer.
Example of a short post.