I have created my own markup language. It’s 4 lines of sed.

s/https?:\/\/[^ ]*[^.!?> ]/<a href="&">&<\/a>/g
s/\[\[(.+)(\/|\.txt)]]/<a href="\1\2">\1\2<\/a>/g
s/\[\[(.+)]]/<a href="\1.html">\1<\/a>/g
s/\*[^*]+\*/<em>&<\/em>/g