What you usually see
When you read the home page of Gabriolan.ca, you’ll notice that beneath each blog post there’s a comment link. You can click on No comments yet; add yours. to get to the comment form. Or, if others have already commented, that link may say 4 comments so far – click on that and you’ll get to the comment form.

When you’re viewing an individual blog post you can scroll down to the bottom of the page to find the comment form. It will be there if comments are open on that particular post.

What you see when comments are closed
When comments on a post are closed, you’ll see something like ‘comments off’ or ‘comments are closed’ (depending where you are on the site) instead of having access to the comment form. Or, if you’re reading an individual post and any comments it has received, there will be no comment form at the bottom of the page.
Why are comments closed?
The most common reason: to reduce comment spam.

We’ve set our blogging software to automatically close comments when a post reaches a certain age. So, for example, it will close comments on all posts that are older than 30 days, or 15 days, or 60 days, or 2 days – whatever we choose.

This is to reduce the amount of comment spam we get. You don’t see the spammy comments because we don’t publish them, but they arrive every day nonetheless. Our spam-catching software puts them into a special ‘spam’ folder for us, and then we delete them. If spammers have thousands of blog posts to target when they arrive at Gabriolan.ca, we might get thousands of spammy comments. Giving spambots lots of opportunity to submit comments is likely to slow the site down somewhat, so closing old comments makes sense to us.

When we get hundreds of spammy comments in an hour, we usually set the expiry date on old posts to be, oh, a week or so after a post is published. When we’re not getting so much spam, we might change it so that comments are open for a month or so on old posts.

When legitimate commenters (i.e. not spammers!) are discussing something that’s important to Gabriola (like the discussion we had about the 2011 election, for example), we change the settings so that the discussion can continue until the election is over and the discussion has died down.

Another possible reason:
The blogger ( see list of people who blog on Gabriolan.ca) can choose not to enable comments on a specific post. I can’t think of a time when that’s happened here, but I suppose that might have occurred sometime or other in the history of this blog.
And so…
If you have something to say, do post your comment soon-ish. If you wait until next month, the comments on that particular blog post will likely have closed.