How to write constructive comments

I've spent many years on this website with different accounts and it seems, that many users still don't know, how to write proper questions under an item post or to write at least some useful thoughts.

Under this topic I would like to collect some productive ideas as an intent to bring back quality comments to this site.

As a prime example I would like to use the comment section of an fictive vest with patches, as these items receive usually the most comments.

These suggestions ARE recommendable:
- If you like the vest, write a positive feedback to the user, but do not forget to write, why this vest is in your opinion a good one, or what makes this vest so special for you in the first place.
- If you don't like for example the result of the sewing or the placement of the patches on this vest, just write to the user your personal ideas, how it could be done better in the future and please don't forget to write, how your suggestions can be effectively achived.
- Always write your questions, if you would like to know something about this item. For example, you would like to know, where the user got the patches / buttons / the vest itself etc., just ask the person about it.

These suggestions ARE NOT recommended:
- If you do not like the bands or symbols on the vest itself for irrational reasons, that your own musical, artistic, political or philosophical taste is superior to the user in question, never accuse someone because of it. Everyone has their own beliefs and opinions, just accept this fact and ignore it, as this website was not designed for the discussion of such topics in the comment section.

- NoMeansNo. If a user didn't would like to sell or trade the patches on their vest, do not further try to convince him to do so with offerings and so on. You can avoid such questions, when you look at the top right of the screen, where it is written, if this item is for trade, sale or not.

- Do not comment 'price?' on posts that are for sale, there's a whole sentence above the comment box on never discussing prices or buying in the comments which often gets overlooked (small suggestion maybe make that text white instead of grey so it stands out).

- Do not write comments on archive posts asking about trades or sales, it's an archive account. It isn't a real user who will reply, its just an account for archiving old deleted posts. Have questions about the patch, its manufacturer, etc, sure, but you are relying on another user to potentially see that and reply to you.

If you feel, that you're unable to deal with such simple advices, maybe it is time to abandon your account on this site and to surf on a social media site of your choice, where you can get your 15 minutes of fame in your safe space.

Please write your own suggestions, as I would like to collect them in these two lists.