I've just deleted a comment that didn't even pretend to be about the post it purportedly commented: it was just a crappy ad for some crappy product or other.
Just to be clear: everyone is free to comment here. I won't delete comments because they contradict or even attack something I write. I don't mind strong language, and if you are not politically correct, fine with me. If your (cogent) comment contains a link to your web page, so be it: I have no problem with it.
However, if your comment is of the "Nice post! For a really excellent whatever check our website" variety, either try to articulate why your whatever should interest the readers of that specific post, or don't comment: your comment will be deleted as soon as I see it.
Also, if you are a translation company, you are very welcome to comment here, but if it looks like the sole purpose of your comment is to drive readers to your website, I will probably delete your comment (again, I won't delete your comment if it has something to say about the post to which it is attached).
On the other hand, sometimes comments are not displayed immediately. That might happen for two reasons: if the comment is to an older post, I need to approve it before it is displayed (the reason for this is that I found that most comment spam goes to older posts, not newer ones); the second reason is if Blogger's spam filter judges it as spam: the filter is not perfect, and sometimes it quarantines legitimate comments; in that case I will have to rescue the comment from the filter and approve it, before it is published.