Created using remix-ide: Realtime Ethereum Contract Compiler and Runtime. Load this file by pasting this gists URL or ID at https://remix.ethereum.org/#version=soljson-v0.4.23+commit.124ca40d.js&optimize=false&gist=

forum.sol

pragma solidity ^0.4.0;
contract Forum {

    uint16 constant maxValue = 10000;//when currentValue>maxValue let currentValue=currentValue%maxValue
    uint16 currentValue;//increase by 1 in every Publish/Comment, and set item.valueSend with it as locater in current block
    
    struct User {
        address addr;
        uint weight; //used to exercise his rights
        string name;  
        string photo; //can be a url of your photo image
        string words; //sth you want to show
    }
    
    struct Item {
        uint id; //index in items
        
        address author;
        
        //bytes32 txHash; //hash of tx which contains the data
        //there is no way to get current tx hash to locate the item,
        //now we use ( blockNumber, author address, value send in the tx) instead
        uint blockNumber;
        
        uint16 valueSend; //used to locate the item
        
        bool isRoot; // if this item is a article
        uint parent; // if it is not root, its a comments of a article or other comment
        
        uint approve; // num of people who approve this item
        uint opposition;//num of people who opposite this item
        
        uint[] comments;//index of the comment in items
    }

    User[] public userList;//all users
    mapping(address => uint) users;// relation from address to user
    
    Item[] public items;//all articles and comments, identifed by its index in this array
    Item public latest;
    mapping(address => uint[]) userItems;//relation from user to its items
    
    event publishDone(address author, string article, bool isSuccess);

     function signIn(string name, string photo, string words) private {
        uint len = userList.length;
            userList.push(User({
                    addr: msg.sender,
                    weight: 0,
                    name: name,
                    photo: photo,
                    words: words
                }));
            users[msg.sender] = len;
    }
    
    function signInIfHaveNot() private {
        uint idx = users[msg.sender];
        if (  idx <= 0 ){
           signIn('','',''); 
        }
    }

    ///register with your address and edit your info{name: $(name), words: $(words), photo: $(photo)}
    function setUserInfo(string name, string photo, string words) public{
        uint idx = users[msg.sender];
        if (  idx <= 0 ){
            signIn(name,photo,words);
        }else {
            userList[idx].name=name;
            userList[idx].photo=photo;
            userList[idx].words=words;
        }
    }

    /// Publish your article
    /// Note that you should convert it to byte[] with utf-8 encoding.
    function publish(string article, bool isArticle, uint parent) public {
        signInIfHaveNot();
        
        if ( msg.sender.call.value(currentValue)(article) ){
            uint len = items.length;
            //use send value as article id
            latest = Item({
                blockNumber: block.number,
                approve: 0,
                opposition: 0,
                id: len,
                valueSend: currentValue,
                isRoot: isArticle,
                parent: parent,
                author: msg.sender,
                comments: new uint[](0)
            });
            items.push(latest);
            userItems[msg.sender].push(len);
            currentValue++;
            if (currentValue >= maxValue){
                currentValue = currentValue % maxValue;
            }
            emit publishDone(msg.sender,article,true);
        }else{
            emit publishDone(msg.sender,article,false);
        }
    }

}