Why do some things work only offline in Editing Mode?

[kr1egsgott]

Like Height-Mapping or Blendmapping.
Is there a technical reason behind?

[TheLastProject]

I believe it is due to there being no code to synchronize those changes. At least, that is what I've been told.

[qreeves]

If you've ever edited a large map and had someone come in and modify a whole bunch of cubes all at once, you'd know why things like this aren't allowed. Height-mapping would prohibitively slow down network and the clients processing the incoming messages (due to high volume), blendmapping simply has no way to synchronise well, as it is stored in the lightmaps (which also aren't synchronised except via sendmap).

[Dan the Man]

But what about undo/redo, at the very least?