So you want to post a comment? Cool. Comments are HuSi's lifeblood.
There really isn't a great deal of difference between them, except for the links you have to click on in order to get started.
To post a Top-Level comment, look for the link saying "Post A Comment", after the main body of the story/diary, in the line including the comment summary for the story/diary.
To post a Child / Sub-Level comment, first find the comment to which you want to reply. Underneath every comment is a little options bar which contains a link which says "Reply to This". Click it.
When you reach the comment posting page, you should see a form consisting of two fields. The 'Subject' field is for the title of your comment, or for very short, pithy comments. The 'Comment' field is for the bulk of your comment. You do not have to fill in the large 'Comment' field, but you must put some contents in the short 'Subject' field.
Underneath the 'Comment' field, you can select the formatting method. The options are: Html Format, Plain Text, and Auto Format. If you select Plain Text, your comment will be posted as you have typed it.
When your comment masterpiece is complete, click 'Spellcheck' to check it over before you post, and see how it will look. If you want to see how your comment will look without checking the spelling then click 'Preview'.
After you click 'Post', the comment will be displayed to you, and the page will say "Comment posted! Thank you for contributing.".
[ Important Note: If you click 'Post' and the page does not reload in a reasonable time, try not to click 'Post' again immediately. If you do this you will get a [Form Key Error]? warning. This means that your comment has already been submitted, and pressing Post might result in a duplicate comment. If you get this warning, open another browser tab or window and navigate to where you were trying to post your comment. If your comment is not there, wait until your posting page has timed out, check that the comment still hasn't been posted, and try again. This can happen if the page seems to have frozen and you click post again. Do not worry if you end up accidentally posting duplicate comments. It happens every so often and is not the end of the world. HuSi's resident editors will usually tidy it up. ]
Many people, if their comment uses the 'Subject' field only, will put [nt] or [n/t] at the end of the subject line, in order to indicate that there is no text in the main 'Comment' field (this is so that people using minimal viewing options will know that they don't need to open the comment fully, because there's nothing there). A smaller number of people will often lie about this. This isn't a rule, just a custom, and you will often see various forms of nt used in the subject-lines of comments around the site.
[ Note: If you are going to put a lot of work into your comment, story or diary, it is often better to write it in a text editor (such as Notepad, TextPad, Kate, NEdit or Vim) and then copy the text over into the 'Comment' field. This will protect you from the delightful quirks of the modern web browser, should anything go wrong. For example: Some browsers will not 'remember' the contents of your comment, if you have to go 'back' for any reason; Also, text editors will remind you if you are about to close a window whose contents have not been saved - web browsers will not. Many fair and beautiful comments have tragically and prematurely died in such accidents... ]
You can select the signature behavior for your comment, there are three options: