user-1: I've recently lost to a 1500 player. My rating is about 1200. Ironically, he got 163 points. How is it possible for a 1500 player to gain more points on a lower-rated player? The system that Lichess uses to calculate rating scores is very confusing. How is it done?

user26335: Without the link to player profiles and the game iteself, it is difficult to say for certain exactly what happened.
For one, Lichess starts new users with a rating of 1500.[1]
Even if your opponent didn't have a 1500 rating, as double-beep points out Lichess uses the Glicko-2 rating system[2] which explicitly tracks the player's rating, a rating deviation, and a rating volatility. The system views a player's rating from a stochastic perspective, as an interval not a single point value.[1]
The system will detect and provide a larger rating change in various circumstances including:

"exceptionally strong results after period of stability",[3] or
after a period of inactivity (it is less certain if rating is still accurate).

The Glicko-2 creator, Dr. Mark Glickman, provides the mathematical formulas for the system.[3,4]
As an example, consider this classical game on Lichess. At the time of the game, the player with the White pieces had only played 1 rapid game. The system seeded the player (White) with a 1500 rating but annotated it as 1500? to denote the provisional rating.
References:
[1] Chess Rating Systems, Lichess website.
[2] What rating system does Lichess use?, Lichess FAQ page.
[3] Example of the Glicko-2 System, ME Glickman, 30 Nov 2013.
[4] http://www.glicko.net/glicko.html, website by Mark E. Glickman.

-1: <p>I've recently lost to a 1500 player. My rating is about 1200. Ironically, he got 163 points. How is it possible for a 1500 player to gain more points on a lower-rated player? The system that Lichess uses to calculate rating scores is very confusing. How is it done?</p>
 26335: <p>Without the link to player profiles and the game iteself, it is difficult to say for certain exactly what happened.</p>
<p>For one, Lichess starts new users with a rating of 1500.<sup>[1]</sup></p>
<p>Even if your opponent didn't have a 1500 rating, as <a href="https://chess.stackexchange.com/questions/38699/how-is-rating-score-calculated-on-lichess/38700#comment61678_38699">double-beep points out</a> Lichess uses the Glicko-2 rating system<sup>[2]</sup> which explicitly tracks the player's <strong>rating</strong>, a <strong>rating deviation</strong>, and a <strong>rating volatility</strong>. The system views a player's rating from a stochastic perspective, as an interval not a single point value.<sup>[1]</sup></p>
<p>The system will detect and provide a larger rating change in various circumstances including:</p>
<ul>
<li>&quot;exceptionally strong results after period of stability&quot;,<sup>[3]</sup> or</li>
<li>after a period of inactivity (it is less certain if rating is still accurate).</li>
</ul>
<p>The Glicko-2 creator, Dr. Mark Glickman, provides the mathematical formulas for the system.<sup>[3,4]</sup></p>
<p><strong>As an example</strong>, consider <a href="https://lichess.org/LElAJZxq" rel="nofollow noreferrer">this classical game</a> on Lichess. At the time of the game, the player with the White pieces had only played 1 rapid game. The system seeded the player (White) with a 1500 rating but annotated it as <em>1500?</em> to denote the provisional rating.</p>
<p>References:<br />
<sub>[1] <a href="https://lichess.org/page/rating-systems" rel="nofollow noreferrer">Chess Rating Systems</a>, Lichess website.</sub><br />
<sub>[2] <a href="https://lichess.org/faq#ratings" rel="nofollow noreferrer">What rating system does Lichess use?</a>, Lichess FAQ page.</sub><br />
<sub>[3] <a href="http://www.glicko.net/glicko/glicko2.pdf" rel="nofollow noreferrer">Example of the Glicko-2 System</a>, ME Glickman, 30 Nov 2013.</sub><br />
<sub>[4] <a href="http://www.glicko.net/glicko.html" rel="nofollow noreferrer">http://www.glicko.net/glicko.html</a>, website by Mark E. Glickman.</sub></p>
