Czuch:  Theoretically the players' ratings at the end of a match should be more indicative of their "true" ability than their ratings at the beginning, since being later in time they should reflect a larger statistical sample (i.e. more games played).  Remember your own rating will also change during the term of a match.  This is just a feature of a turn based site you can't do anything about.

One thing I have noticed that might be fixed is in setting the BKR range for a tournament.  Eligibility is based on a player's rating at the time he or she joins the tournament.  At the time the tournament starts, his or her rating may be significantly lower than the eligibility threshold.   This  diminishes the utility of being able to set a minimum BKR for entry.  This would not be particularly important if the BKR system for backgammon worked properly, but it does not so this is a major problem.