the forum might be a mess if such meaningless posts are ignored.
If we have 100 users posting like that repeatedly, then that is an issue that needs to be handled. One user doing it once in a while is not such a disturbance.
And there's a difference between unreadable, and one struggling to read it. If I can make sense of the post or the idea the user is trying to pass across, it's fine with me.
What Mr A view as quality post, may be a spam to the other person, and regardless whether the wall of text is large or not, as long as it carries a message that I can relate with and to, it may look as not spam post for me even when others but with just one person reading and understanding it, the posts will be seen as a neutral quality, because at that point of views that can read and understood by the other party, just as upgrade mentioned above.
The issue of spam post or low quality post's is somewhat an individual things as last Ng as the post already meet the forum standard, the quality rating after then will be individual subjective case