Disregarding content & only considering style I think a good, easy to understand post needs in order of importance:
- Correct spelling
- Correct capitalisation
- Well placed commas & full stops
- Blank space between paragraphs
If you can manage that you won't go far wrong.
I like a good interrobang as much as the next man but I often find readability decreases as the amount of punctuation increases. Try to use the smallest character set possible.
Don't join two ideas with 'and', write two separate sentences.
You can't beat a good combination of varying sentence lengths.
There are exceptions to every rule!