I'm using Google Chrome 77.0.3865.90 (latest version of Stable channel) on Windows 7 SP1. I tried double-clicking words on the search bar of a search results page ([[https://en.wikipedia.org/w/index.php?search=(They%20Long%20to%20Be)%20Close%20to%20You&title=Special%3ASearch&fulltext=1 | example 1]], [[https://en.wikipedia.org/w/index.php?search=Hensuki%3A%20Are%20You%20Willing%20to%20Fall%20in%20Love%20with%20a%20Pervert%2C%20as%20Long%20as%20She%27s%20a%20Cutie%3F&title=Special%3ASearch&fulltext=1 | example 2]]; [[https://en.m.wikipedia.org/w/index.php?search=(They%20Long%20to%20Be)%20Close%20to%20You&title=Special%3ASearch&fulltext=1 | mobile 1]], [[https://en.m.wikipedia.org/w/index.php?search=Hensuki%3A%20Are%20You%20Willing%20to%20Fall%20in%20Love%20with%20a%20Pervert%2C%20as%20Long%20as%20She%27s%20a%20Cutie%3F&title=Special%3ASearch&fulltext=1 | mobile 2]]) to highlight the words. Somehow, I instead highlighted different words instead of the ones that I want to specifically highlight/double-click on. The problem is not limited to Wikipedia. I tested out the bar on other projects, like Commons; similar issue.
On the other hand, I tested out the words at IE11, and double-clicking the specific words works well there. Also, I can highlight the words on the search bar well via Apple Safari and [[https://en.wikipedia.org/wiki/Samsung_Internet | Samsung Internet Browser]] (haven't tried this on Mozilla Firefox yet). I don't know why specifically Google Chrome has that problem on both desktop and mobile.