Kinda weird question:
Soo, according to

mysql 5.0.3 and up can store 65,535 characters in a varchar type (which is the type set for the t_string table). Substract 2 bytes for the length of the string, so 65,533 characters is the maximum you can have in your database.
255 if you're using an older version, which you shouldn't. Also note that by default, 255 is set as the maximum length, at least in my table. You should be able to set that value up to 65k though.
The .lod file can contain anything (as long as your exporter exports everything), however the client only provides a 8192 byte-sized char array, which results in 8192 being the maximum number of characters a single string can hold by default.
See Engine/Help/Loader/Loader.cpp -> bool TableLoader::load_file( const char* str_path, int strCnt ) for details.