Problem with forum tagging

It appears that it is almost impossible to tag users on forum posts now because only three options are given and they invariably do NOT include the person one is attempting to tag.

For instance, for John Smith, if one types John , then the three options might be John Jones, John West and John Black. One then types Smith and is given the option of Mary Smith, David Smith and Peter Smith, but NEVER John Smith who should be obvious to their system as he posted the post immediately above.

This is most annoying and I don't know how to tag the right person any more.

Thank you.

Jacqueline.