It actually centers the image in legacy, flat, and book. Not in web.
I'd be inclined to suspect something like (inline-)block more than text-align.
Edit: I can confirm that it works fine if you minimize it to just a text-align testcase. I don't have time to figure out where the problem comes in precisely though. I'm not sure if inline-block is actually supported; it could be as simple as that.
Simplified test:
Code:
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<title>The Author</title>
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<div class="chapter-title" style="text-align:center"><div class="chapter-title-decoration-above"><div class="chapter-title-decoration-above-inner"><img alt="image" class="chapter-title-decoration-above" src="./OEBPS/Images/chapter_title_above.png"/></div>
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<h1 class="chapter-title">The Author</h1>
<div class="chapter-title-decoration-below"><div class="chapter-title-decoration-below-inner"><img alt="image" class="chapter-title-decoration-below" src="./OEBPS/Images/chapter_title_below.png"/></div>
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<p class="first-in-chapter"><span class="first-chapter-phrase"><span class="first-in-chapter character-s">S</span>TEPHEN BUTLER LEACOCK</span>(December 1869 – March 1944) was born in England and moved to Canada when he was six years old. He became a Canadian teacher, political scientist, writer, and humorist.</p>
<p>Early in his career, Leacock turned to fiction, humour, and short reports to supplement (and ultimately exceed) his regular income. His stories, first published in magazines in Canada and the United States and later in novel form, became extremely popular around the world. It was said in 1911 that more people had heard of Stephen Leacock than had heard of Canada. Also, between the years 1915 and 1925, Leacock was the most popular humorist in the English-speaking world. </p>
<p>Leacock died of throat cancer in Toronto in 1944. A prize for the best humour writing in Canada was named after him, and his house at Orillia on the banks of Lake Couchiching became the Stephen Leacock Museum.</p>
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