When using Arcpy you are able to use funtions like arcpy.AddMessage to print statements in the geoprocessing result messages. I believe there should be a nice simple and built-in way to do this within ModelBuilder so people are able to troubleshoot. It could be kept simple at first and utilize outputs that are already being made like counts from select geoprocessing, so you can add a message for the count.
Ultimately though I think we should be able to add any message we want just like we are able to in python and also be able to utilize error messages too.
Also I realize that there is a custom way to do this by creating a script tool and adding it to the model, but this should be built-in to modelbuilder.
