There's been no change between versions with regards to this aspect of FileMaker. The delete portal row script found in the Known Bugs List, for example, has continued to function correctly when the file was converted from .fp7 to .fmp12 and continues to function correctly with FileMaker 13.
Check and make sure that the portal setup option to permit portal row deletion is enabled if you are using the Delete Portal Row script step to delete the portal record, but what you report with Get ( ActivePortalRowNumber ) suggests that something is causing the clicked portal row to lose focus. Commit records is definitely a prime suspect, but maybe you have a script trigger that is also being tripped when you attempt to use this script to delete a portal row?
your so sharp ! there was a script trigger linked to portal that disrupted deletion. can you point me to knowledge as to the hierarchy of commands and triggers. I debugged several times never considering such as being cause for disruption.
Any script that interacts with the layouts may trip a script trigger. When such is tripped, the script that trips the trigger is paused, the trigger performed script runs to completion and then the paused script picks up where it left off--unless it ends with "Halt Script", in which case all paused scripts are halted right where they were paused.
It's often useful to use a global vairable as a flag. All trigger performed scripts check the value of the variable and exit without doing anything if the script is set. You can then disable all trigger controlled scripts by setting the variable to a value.