There is no standard for the representation of a pencilmark grid in a line format. The 729-character line representation has benefits but having delimiters will certainly shorten the lines in most cases. In the Sukaku explainer project we are working on at the moment we are using the 729-character line and the multi line pencilmark grid. So it appears that the 729-character is becoming more of a standard as more people use it.
If you are using delimiters especially spaces may have issues with sharing and posting them as you can’t control how the message board formats them. The 729-character line has less problems in the way.
We are currently working on a project on github to improve Sudoku explainer and allow rating of Sukaku. The puzzles I posted remain challenging without a rating as we speak because of the time required to process even a single elimination
Tarek