A play on words meaning, of course, that Document Mode is more important than Thread Mode but suggesting also to put Summaries On Top Discussion Below.
I have done my best to discourage dialog in favor of dissertation which offers a better fit to this medium. -- Ward Cunningham on Wiki History
Over the course of time dialog has often been exchanged for "discourse" when referring to this now famous quote. It will be worth the reader's time and effort to read the full quote in context. Because the dictionary definitions of these terms fail to make a clear distinction between the two, the following definitions are humbly offered for purposes of Wiki On Wiki discussion:
Dissertation:
a unified presentation of ideas, as if from a single mind although joint authorship accepted and encouraged, in which arguments are made, information presented, instructions or advice given, etc., with concomitant assumption of authority over the chosen subject matter. [Document Mode] Encourages linear thinking
Discourse:
a multi-part exchange of ideas, information, advice, admitting questions and answers, in which two or more distinct minds interact in order to explore subject matter jointly, where authority is not an essential ingredient but when present is usually distributed and often conflicting. [Thread Mode]
Encourages recursivity, unpredictable
Well-composed dissertation pages create starting points for further consideration. On FedWiki, those points can be indicated using stubs. Linked dissertation pages can be used to create an ever-widening Radical Discourse that Thread Mode doesn't.
On Wiki Wiki Web, Dissertation is generally more highly valued than Discourse because it is thought to be more readable. Discourse is seen by some as a means to achieve the more preferred end of Dissertation. Dissertation establishes a page as a point to depart from and link to, a node in a discourse that can be developed, built on, rethought, revised. A well-wrought Dissertation page will function as Adorno envisions it
Adorno start quote
Properly written texts are like spiders’ webs: tight, concentric, transparent, well-spun and firm. They draw into themselves all the creatures of the air. Metaphors flitting hastily through them become their nourishing prey. Subject matter comes winging towards them. The soundness of a conception can be judged by whether it causes one quotation to summon another. Where thought has opened up one cell of reality, it should, without violence by the subject, penetrate the next. It proves its relation to the object as soon as other objects crystallize around it. In the light it casts on its chosen substance, others begin to glow.source 
end quote
Alan Levine describes the Fedwiki as a set of index cards. That might lead one to think in terms of dissertation, but the way index cards work tends to involve an interaction between cards as the warp and weft of the arguments is woven together. This process is a kind of dialogue. What seems valuable about fedwiki is the potentail for this kind of exchange. The degree of granularity is important perhaps.
See also: Dissertation Favored Over Dialog, What Is Thread, Thread Mode, Document Mode, Dialectic Mode
What we might have given up in Rethinking ThreadMode and Rethinking DocumentMode we regain in Radical Discourse. The idea is that when dissertation pages are linked up, constellated, we create the larger, multi-voiced discourse.
See original on c2.com
I am writing this page in response to the Dissertation Over Discourse page. It is not a value-neutral "preference".