注意：私は2021年にこの質問を整理して、デッドリンクを削除し、コードをライブデモにしました。ざっと確認すると、現在のバージョンのChromeには問題がないようです。
行の高さとマージンがnであり、その領域の高さがの倍数でnあり、scrollTopが倍数で増加している領域を考えるとn、Firefox、Opera、NetFrontで期待する結果が得られることがわかります。 Chrome（Windows）、Safari（Mac）、および最新のWebKit nightly（Mac）には多少のリークがあり、部分的な線が表示されます。
私の実際のプロジェクト（共有することはできません）では、効果は非常に顕著ですが、テストケースを減らしても、前の行の下部がボックスの上部から覗いているのがわかります。
この影響を回避することは可能ですか？これは、報告する必要があるWebKitレンダリングエンジンのバグですか？
縮小されたテストケースを以下に示します。ドキュメントを数回クリックしてスクロールします。ボックスの上部にあるドット（前の行の文字の下部）ではありません。
<!DOCTYPE HTML>
<html lang="en">
<head>
<meta charset="utf-8"/>
<title>scrollTop issue</title>
<style>
body {
background-color: white;
color: black;
}
#wrapper {
width: 300px;
font-size: 19px;
font-family: sans-serif;
line-height: 21px;
height: 210px; /* A multiple of line height */
overflow: hidden;
}
#wrapper * {
margin: 0;
padding: 0;
}
#wrapper p {
margin-bottom: 21px; /* Same as line height */
}
</style>
<script>
window.addEventListener('click', function () {
document.getElementById('wrapper').scrollTop += 210;
});
</script>
</head>
<body>
<h1>scrollTop issue</h1>
<div id="wrapper">
<div id="content">
<p>To Sherlock Holmes she is always <i>the</i> woman. I have seldom heard
him mention her under any other name. In his eyes she eclipses
and predominates the whole of her sex. It was not that he felt
any emotion akin to love for Irene Adler. All emotions, and that
one particularly, were abhorrent to his cold, precise but
admirably balanced mind. He was, I take it, the most perfect
reasoning and observing machine that the world has seen, but as a
lover he would have placed himself in a false position. He never
spoke of the softer passions, save with a gibe and a sneer. They
were admirable things for the observer—excellent for drawing the
veil from men’s motives and actions. But for the trained reasoner
to admit such intrusions into his own delicate and finely
adjusted temperament was to introduce a distracting factor which
might throw a doubt upon all his mental results. Grit in a
sensitive instrument, or a crack in one of his own high-power
lenses, would not be more disturbing than a strong emotion in a
nature such as his. And yet there was but one woman to him, and
that woman was the late Irene Adler, of dubious and questionable
memory.
<p>
I had seen little of Holmes lately. My marriage had drifted us
away from each other. My own complete happiness, and the
home-centred interests which rise up around the man who first
finds himself master of his own establishment, were sufficient to
absorb all my attention, while Holmes, who loathed every form of
society with his whole Bohemian soul, remained in our lodgings in
Baker Street, buried among his old books, and alternating from
week to week between cocaine and ambition, the drowsiness of the
drug, and the fierce energy of his own keen nature. He was still,
as ever, deeply attracted by the study of crime, and occupied his
immense faculties and extraordinary powers of observation in
following out those clues, and clearing up those mysteries which
had been abandoned as hopeless by the official police. From time
to time I heard some vague account of his doings: of his summons
to Odessa in the case of the Trepoff murder, of his clearing up
of the singular tragedy of the Atkinson brothers at Trincomalee,
and finally of the mission which he had accomplished so
delicately and successfully for the reigning family of Holland.
Beyond these signs of his activity, however, which I merely
shared with all the readers of the daily press, I knew little of
my former friend and companion.
<p>
One night—it was on the twentieth of March, 1888—I was
returning from a journey to a patient (for I had now returned to
civil practice), when my way led me through Baker Street. As I
passed the well-remembered door, which must always be associated
in my mind with my wooing, and with the dark incidents of the
Study in Scarlet, I was seized with a keen desire to see Holmes
again, and to know how he was employing his extraordinary powers.
His rooms were brilliantly lit, and, even as I looked up, I saw
his tall, spare figure pass twice in a dark silhouette against
the blind. He was pacing the room swiftly, eagerly, with his head
sunk upon his chest and his hands clasped behind him. To me, who
knew his every mood and habit, his attitude and manner told their
own story. He was at work again. He had risen out of his
drug-created dreams and was hot upon the scent of some new
problem. I rang the bell and was shown up to the chamber which
had formerly been in part my own.
</div>
</div>
</body>
</html>