5.14.7. The indentation of my programs is all wrong. Why?

Interscript does not allow tabs. You should never ever use tabs, they're an extremely stupid idea. Interscript replaces tabs by spaces automatically. This feature _cannot_ be disabled (without hackery), because it is implemented in the main control loop.

The variable g.tabwidth can be changed from the default value of 2 (which is suitable for publication) to some other value (such as 8) with a command like @g.tabwidth = 8.

You can, and sometimes must, generate tabs in code files. For example, tabs are required in 'make' files. You can do this in many ways, for example by implementing a front end for a tangler that replaces leading spaces, or perhaps \t sequence, by tabs.