MathML with right-to-left content is not rendered correctly in the content view.
This is an open issue in MathJax, the MathML renderer used by Fonto.
Find and replace "whole word only" checkbox does not work well with words containing special/accented (non-ASCII) characters.
For example searching for "thing" matches "àthing", but searching for "thìng" does not match "thìnga" but does match "thìngà".
Find and replace does not always show its results in the expected order.
Find and replace currently operates in (XML) document order instead of visual order. This affects elements such as footnotes.
The overflow slider in the the masthead has some quirks.
The overflow slider sometimes clips the right border of the rightmost button and behaves unexpectedly if a button group cannot be entirely contained in the view.
Unexpected behaviour for inserting inline formatting like bold, italic, etc. when a schema contains a single element for multiple types of inline formatting.
For example, when a selection starts within bold text, ends outside that bold text and italic formatting is applied, only the non-bold part of the selected text will be italic.