-Short replies don’t help — you need to write like you're helping someone.
I disagree on this, short replies are always direct and straight to to the point and most forum members prefers short posts, they often carry more quality. Most lengthy post usually discouraging to read through and most times they deviate from the point they are trying to make making it difficult for the audience to understand.
-Posts in quiet threads may never be seen — post where readers hang out.
What do you mean by quiet threads? Your post will be seen anywhere in the forum I even believe posts in mega threads are easily missed. Doesn't matter, quiet or busy threads if you have contribution to make you should.
-Original thinking matters — don’t copy anything, not even from your own posts.
With reference link provided you don't have anything to worry about.