There IS visible difference between answer and comment in the word meaning, appearance, content and length. You can have a look at the most answers addressing the questions and to the answers saying just "Good idea", "Thank you", "It worked".
Most of the points were already given by pinkunicorn. As already said in the linked question, the downvote is the last thing to do. I am adding explanatory comment in these cases. If you have more polite comment, please add it. If you do not agree, feel free to comment on the cases where do you think that it is answer.
The baseline is not set in the stone, nor what cases should be handled how. The common understanding in this among most of the users is crucial to handle the cases systematically, ensure some order in this QA and make the site helpful for all the users, not just a dumping area for "It worked" "answers".