Is it necessary to link all posts together?

Link that exist on each post its will help to increase your rank in search engine. You can modify the link inside that match with the main keywords.

It's a pity that there are so many 1 sentence garbage posts to drown out the good information.

Only weblink to another material if they are appropriate or may be of attention to anyone studying the publish, which will be a advantage you cant weblink to every publish as your material develops it will soon become difficult.

Andy, your comment was followed by another one sentence garbage post. It looks like the spammers and content spinners are taking over this thread.