[MilStdJunkie]

Every time you glue on an extension to your markup language - or do a specialization with DITA, or modify S1000D via the BREX, or combine a dozen different MIL-STD DTDs to write your snowflake publication - you've reduced the volume of the tools ecosystem needed to render and write the thing. If everyone does this, you're effectively using a bespoke doc spec for each application, or even for each program or product.

Not all computing platforms allow users to do whatever. Eventually these disparate doc platforms will need to get merged, updated. What happens when Restrictive Platform X needs to update your Special Format? They fork, and they use a doc markup that's workable on a generic platform. Welcome to Double Work Town.

Anyway, it's pretty important to select a markup whose core specification does all the things you need on a generic computing platform[1]. Many different paths branch from that one singular fact, but I'll stand by that singular fact. Seen too many decades flushed down the toilet of churning doc/markup formats.

[1] That doesn't require frickin admin access for trivial writing tasks, like changing DTDs.

<cough>Arbortext</cough>