Content of 9th line displayed partially in Comment field

In order to reproduce this behaviour:

1. enter 8 lines of text into the lower Comment field,
2. hit Enter,
3. start typing content of the 9th line
   Observed : content of the line is being displayed partially.

Expected : field will expand to display the 9th line correctly.

In the same time, the 10th and any next line will expand the field correctly.