CJK characters are broken
Asian alphabets (e.g. Chinese characters) seems broken. The following screenshot shows how scrnshtr took http://hongminhee.org/. Pay attention to the three squares in the title.

It seems rendered well if Chinese characters are styled using web fonts.
@dahlia scrnshtr is using phantomjs to generate the screenshots so I'm not completely sure on what kind of character sets it supports. I'll leave the ticket open till I figure out a solution if one exists for this.
Thank you for pointing this out :+1:
@dahlia I ran into the same problem. I think you can use your font file(.ttf) for Phantomjs on Heroku. Just put it in .fonts dir and git push heroku master. Here is an example :)
