In order to reproduce this behaviour:

1. enter 5 lines of text into the Hover over Comment field,
2. hit Enter,
3. enter 6th line (you experience variation of JRA-22141
4. hit Enter in order to type the 7th line
Observed : content of the 7th line isn't displayed until you navigate between lines or enter some more text into the 7th line.

expanded 7th line:

Expected : field will expand to display the 6th line correctly.