on my n82 the dictionary sort of erases when it is "full?" although my memory is adequate. and it has many weird words in the dictionary. I have had to enter words again and then after a while it forgets then enter again.
v.31.0.016 9-12-8 rm313 nokia n82 (13.01)
The dictionary on the device has limited capacity. Importing or entering a large number of words will cause some of the older entries to fall out in order to make room for the newer ones.
Regarding the strange looking words, do you mind telling us what is the writing language and some of these words?