You can make a mostly empty comment/post using link Markdown

Question

If you type the following in a comment, you can post an (almost) empty comment:

[.](http://about:blank)

Here's an example of that:

.

I've also included an example of that code in the comments of this question.

In posts, since you can use HTML, you can use empty strikethrough to make a completely invisible link (which is useless):

[<s></s>](http://about:blank)

Here's an example of that:

Answer 1

You can also create a new account and upvote yourself.

You can also build castles using <kbd> tags.

So what? Being able to do things doesn't mean you should be doing them, and surely this isn't a bug in the system.