Fixes always white comment body border

src/vs/workbench/contrib/comments/browser/commentThreadWidget.ts

@@ -884,13 +884,18 @@ export class ReviewZoneWidget extends ZoneWidget implements ICommentThreadWidget
 	}
 
 	private _applyTheme(theme: IColorTheme) {
-		const borderColor = theme.getColor(peekViewBorder) || Color.transparent;
+		const borderColor = theme.getColor(peekViewBorder);
 		this.style({
-			arrowColor: borderColor,
-			frameColor: borderColor
+			arrowColor: borderColor || Color.transparent,
+			frameColor: borderColor || Color.transparent
 		});
 
 		const content: string[] = [];
+
+		if (borderColor) {
+			content.push(`.monaco-editor .review-widget > .body { border-top: 1px solid ${borderColor} }`);
+		}
+
 		const linkColor = theme.getColor(textLinkForeground);
 		if (linkColor) {
 			content.push(`.monaco-editor .review-widget .body .comment-body a { color: ${linkColor} }`);