Number of characters in comments tag

Hi, can anyone tell me if there is a limit to the number of characters or words that can be used in the comments tag?

Yes, there is.
But this depends mainly on the tag version.
In V1 the comment must not exceed 30 characters.
In V2 tags I assume that some kind of IT boundary is valid: ususally this is 255, 32000 or 64000 (app.)

Regarding the ID3 tag, the limit for the length of the comment tag-field depends on the version:
ID3v1.0 ... 30 characters (8-bit)
ID3v1.1 ... 28 characters (8-bit)
ID3v2.3 ... don't know
ID3v2.4 ... don't know

You can make a test for yourself.
Note: The function $repeat has a limit of 1000 iterations.

Mp3tag writes to ID3v2.3 tag and can display the COMMENT tag-field in the dialog "Extended Tags...":

$repeat('1234567890',1000) ==> one string of 10 thousand characters

... but got a 'hanging' problem when trying to display the string in an edit field:

$repeat($repeat('1234567890',1000),1000) ==> one string of 10 million characters

DD.20140909.0956.CEST