[trying]

Second Generation Kindle Fire (2012), System Version: 10.5.1
Moon+ Reader Free 4.2.2

I ran across the same problem with "retail" epubs. Everything would be fine when viewing the epubs on my PC using the Calibre E-Book Viewer, but when using Moon+ Reader Free 4.2.2 on a Second Generation Kindle Fire (2012) italics would sometimes (but not always) overlap previous lines. When preparing this post, however, I seem to have stumbled across the cause.

I wanted to post an example epub that only contained two chapters: one that displayed the italics overlap problem and the next chapter that mysteriously did not. Originally I eliminated all the images and kept the entire chapters to create Moon+ Reader Italics Overlap Bug BIG.epub. Then I thought, well, maybe I should instead only show a few paragraphs from each so I created Moon+ Reader Italics Overlap Bug SMALLEST.epub. Much to my surprise, when I tested the SMALLEST epub the overlap problem had disappeared. Since the only thing I did was to make the offending chapter's .xhtml smaller, I wondered if the bug had to do with file sizes.

As it turned out, the chapter that displayed the bug was 22,859 bytes whereas the other good chapter was only 20,321 bytes. And the fixed chapter size was just 4,807 bytes.

So I then created Moon+ Reader Italics Overlap Bug SMALLER.epub and edited the bad chapter down until it was only 19,981 bytes. And yes indeed, the italics overlap problem went away.

When viewing epubs via Moon+ Reader Free on a Kindle Fire, it appears that italics will overlap if an .xhtml file is too big --- bigger than around 20,500 bytes or so.

I have attached all three epubs so you can test this behavior for yourselves.