* *Action 8* Identification of the GRF, can only have some other actions before it.
  Defines the GRFformat (the set of features used by the GRF), an ID, the name, and a description.
>>> Before action 8 appear: action14, and all compatiblity checks/warning/errors (i.e. action b and action e)
>>> A NewGRF cannot error out after action 8.

* *Action 6* Write GRF parameter values into the next sprite (initialization and activation stage).
>>> The difference between initialisation and activation is irrelevant when not using the "add"-mechanism, which is pretty pointless.

* *Action 12* Define Unicode glyphs in sprites following this action.
>>> Belongs rather into the "Replace sprites from the baseset" section

* *Random action 2* Use random numbers for deciding switched.
  Also defines re-randomize behaviour.
>>> The re-randomisation is the only reason this still exists. Deciding is done better via VarAct2.

* *Action E* De-activate other GRF (not supported by OpenTTD).
>>> Deactivation is supported, though disencouraged (i.e. still useless). What is not supported is "force activation" (= activation in title screen)

* What is 'variable 10' doing in http://newgrf-specs.tt-wiki.net/wiki/Action2/Vehicles ?
>>> Variable 10 and 18 are "callback specific" variables. "Resolving graphics" and "rerandomisation" should be just considered another callback.

* Why is action 2 'entries...' a Word (syntax table).
>>> Original reason: Early TTDP (and sometimes still current TTDP) writes the parsing result of NewGRF into the same place as the input. In particular it overwrites some fields in the actions with pointers/references to other items, like assiging all Action2 a unique 16bit id (instead of the reused 8 bit ids). That's why TTDP needs some "space" in some actions, and that's why there are grf loading stages and why action 7 and 9 can only skip certain actions (they may not skip setting up references in the sprites, else TTDP crashes later when trying to follow them)
>>> Todays reason: Action1 can have more than 256 sets. And action1 actually supports "callback result" values.