I think that was suggested a long time ago, for mIRC to warn the user if their line is too long for the editor.
A few suggestions might be:
- Use a 'beep' similar to when a line is too long in the channel editbox
- A warning dialog, stating that the line is too long.
- Or an automative system, where the editor automatically appends a $& and drops the end of the line to the next.
/me shrugs