Is there a maximum-number (integer part) limit when reading X,Y,Z coordinates from i.e. ASCII point-cloud file? (Example: 55000000.123 65000000.123 87000000.123)

As for scaling the model, there is not a hard limitation.  However, larger numbers will affect graphics and some operations where truncation can happen within the algorithms.  Technical Support recommends scaling down the model.

In App Button>Options>File I/O>General, set the Default Precision to specify the accuracy of the floating-point data. This affects how points are loaded. Single precision numbers have 7 digits of accuracy and Double precision numbers have 15. You may also accept the precision that is set in the file that is loaded.

VERSION 11

In version 11, this option is located under Tools>Options>FileI/O>General.