by AL Rachels.
Hi George,
Since some comments are in one location of Moodle, and in another location of another Moodle version, AND there is more than one module that uses comments, it would help to know which Moodle you are using and where the comments at.
Also, since it is going to be controlled by the database field type, might need to know what type of database your Moodle is running on.
Just a quick look through my Moodle 2.3+ on MySQL with phpMyAdmin shows assignmentsubmissions comments and assignment feeback comments as being longtext which is 4,294,967,295 (2^32 - 1) characters or, 4GB.
AL