Questions and answers relating to data models and OO design are often greatly improved by a simple diagram. I want to propose the idea of having something like asciiflow integrated into the editor on SO for creating diagrams.
As a totally arbitrary example; the second answer down on this question makes the data structure he is suggesting almost immediately apparent, without having to construct a mental image from a wordy description.
Something like this could be abused - creating pointless diagrams just because there is the facility to, however this could easily be dealt with by having a new flag for 'irreverent diagram'. This would put an extra little bit of strain on the moderators but I think it would be worth that extra effort for the clarity and quality it would provide to truly suitable questions.