[development] One-to-one tables considered harmful

[Karthik]

> Please explore how Drupal core functions before you make such claims.
> The tables exist for all core modules regardless of whether they're
> enabled or not. So, it is irrelevant that comment is an optional module.

These are being addressed as system.install is being split into
appropriate install files. In other words, the fact that these tables
are being created regardless of their use, is wrong and is being
fixed.