There is no downvote as far as I know. The flag allows you to mark the post as “off-topic” or “other” (and this allows you to give more insight) but I assume this is not exactly what you are searching for.
Although is different, one interesting functionality is that when the post is very long (now 30+ messages), there is a “summarise this post” button that will make a shorter version with the “most relevant” messages. The likes of the messages impact this as well as other factors.
The minimal length of the titles and the messages is configurable. We are using defaults for now. The reason is to avoid very short titles that are not descriptive (think when there is a lot of people this could be a problem). We can change the limit or remove it.