mastodon/app/javascript/styles/closed-social/timeline_comments.scss

.comments-timeline {
	max-height: 160px;
  min-width: 60%;
	overflow: hidden;
	-webkit-mask-image: linear-gradient(#1a1a1a,transparent);
	mask-image: linear-gradient(#1a1a1a,transparent);
	transform: scale(0.85);
	transform-origin: 100% 0%;
	margin-bottom: -32px;
  position: absolute;
  z-index:9;
	&:hover {
	  max-height: none;
		-webkit-mask-image: none;
		mask-image: none;
    z-index:99;
    background: $tc-background;
	}
	&:active {
	  max-height: none;
		-webkit-mask-image: none;
		mask-image: none;
    background: $tc-background;
	}
}

.comments-timeline__wrapper {
  height: 135px;
}