Fix #77663. first comment of a thread should have an unique id.

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

@@ -23,7 +23,7 @@ export class CommentsDataSource implements IDataSource {
 			return `${element.owner}-${element.id}`;
 		}
 		if (element instanceof CommentNode) {
-			return `${element.owner}-${element.resource.toString()}-${element.threadId}-${element.comment.uniqueIdInThread}`;
+			return `${element.owner}-${element.resource.toString()}-${element.threadId}-${element.comment.uniqueIdInThread}` + (element.isRoot ? '-root' : '');
 		}
 		return '';
 	}

src/vs/workbench/contrib/comments/common/commentModel.ts

@@ -21,6 +21,7 @@ export class CommentNode {
 	comment: Comment;
 	replies: CommentNode[] = [];
 	resource: URI;
+	isRoot: boolean;
 
 	constructor(owner: string, threadId: string, resource: URI, comment: Comment, range: IRange) {
 		this.owner = owner;
@@ -28,6 +29,7 @@ export class CommentNode {
 		this.comment = comment;
 		this.resource = resource;
 		this.range = range;
+		this.isRoot = false;
 	}
 
 	hasReply(): boolean {
@@ -55,6 +57,8 @@ export class ResourceWithCommentThreads {
 			commentNodes[0].replies = commentNodes.slice(1, commentNodes.length);
 		}
 
+		commentNodes[0].isRoot = true;
+
 		return commentNodes[0];
 	}
 }