We are all guilty of it and I know the Eastern form. Many do it because they say Mr X not X San, and that then slips in to Sensei X not X Sensei. When using a Japanese title we should write it the correct way round, but hey, does it really matter? If X is an awesome Aikidoka and teacher, does it matter if he is refered to as Sensei X or X Sensei?
Remember that a lot of people in the US use the term Aikidoist in place of Aikidoka, but does that have any effect on their Aikido?
The later is more a pet hate of mne than the former!!!