On a serious note, yes not all syntax noted in the Mermaid docs work yet. I'm planning on adding more coverage of the Mermaid syntax over time. For now the basics work and (hopefully) shows its potential.
Thanks for the feedback! I agree that the web UI can be improved (quite) a bit, most of my efforts went into the actual generation of the diagrams. I'll have a look at prettifying it.
Your policy is blocking ptrace from processes that don't seem like they should need ptrace (very few processes need ptrace). So why would Firefox need ptrace? Some cursory googling suggests that ptrace is used for plugins and by the crash reporter.
PS: it's open source so feel free to help out ;) https://github.com/AlexanderGrooff/mermaid-ascii