After using this system for a while, I realised it missed few things.
First: images. Written just like links, but with curly instead of square brackets. I felt like links will be enough, but website looks better with pictures.
Second: html escaping. While writing b-log on my new guestbook, I realised that I can't write example html in blocks. It was a quick fix in to-html.rb. Just escape '<', '>', and '&' at the beginning.
Third: links. Since ptts is now both ruby and crystal project, I want to put it in both. I chose to use links because there is already too much files generated for single b-log entry. It is not ideal, but it works just enough to pass for now. links are marked by '~>'.
Should be enough for now.