[SillyStegosaurus]

Alright, I installed the RemoveInlineStyles plugin to Sigil and opened an epub Calibre made from the original az3w.

"This EPUB has HTML files that are not well formed or are missing a DOCTYPE, html, head or body elements. Sigil can automatically fix these files, although this may very rarely result in minor data loss in extreme circumstances.

Do you want to automatically fix the files?"

I had it automatically fix the files, then applied the plugin to it. According to the output, no inline styles were found at all!

Checked the epub's stylesheet.css:

Spoiler:

".calibre {
display: block;
font-size: 1em;
padding-left: 0;
padding-right: 0;
margin: 0
}
.calibre1 {
display: block
}
.calibre2 {
display: block;
margin-bottom: 0%;
margin-top: 0%;
orphans: 0;
text-align: center;
widows: 0
}
.calibre3 {
-aw-left-pos: 46.45pt;
-aw-rel-hpos: column;
-aw-rel-vpos: paragraph;
-aw-top-pos: 0;
-aw-wrap-type: inline;
height: auto;
width: 80.29%
}
.calibre4 {
display: block
}
.calibre5 {
display: block;
margin-bottom: 0%;
margin-top: 0%;
orphans: 0;
text-align: center;
widows: 0
}
.calibre6 {
-aw-left-pos: 18pt;
-aw-rel-hpos: column;
-aw-rel-vpos: paragraph;
-aw-top-pos: 18.6pt;
-aw-wrap-type: inline;
height: auto;
width: 92.31%
}
.calibre7 {
-aw-left-pos: 76.7pt;
-aw-rel-hpos: column;
-aw-rel-vpos: paragraph;
-aw-top-pos: 0;
-aw-wrap-type: inline;
height: auto;
width: 67.31%
}
.calibre8 {
font-size: 0.75em
}
.calibre9 {
font-size: 0.75em;
text-decoration: none
}
.calibre10 {
font-size: 0.75em;
font-style: normal;
font-variant: normal;
text-transform: none
}

"

Not really sure how to make sense of this. The epub I got from converting azw3 -> mobi -> epub is so far the only readable epub.