[SOLVED] Backspace causes text shrinkage

[Ytrojan]

I think I found the reason why the shrinkage problem exists
Every time I delete text, the text changes to a smaller size. Eventually, it becomes the size of a single celled organism. This might be a bug, and I'm posting it here because I realized that the editor was broken this whole time. It only happens when I reduce the number of lines of text in the post, which is broken, and is starting to get on my nerves. Let me show you an example.
[size=78%]ALL HAIL THE YTROJAN EMPIRE[/size]
It's clearly broken, and it is in grave need of repair.

[MonkeyIsland]

You are the only one with this problem. Find this icon on top-right of the editor and click on it.

[Ytrojan]

You are the only one with this problem. Find this icon on top-right of the editor and click on it.

Oh, now it works.