I am using line separators in the SeaGlass L&F and had recently noticed that in my JTextArea, there are line separators between the lines.

How to remove line separators from JTextArea in SeaGlass L&F?
I am using line separators in the SeaGlass L&F and had recently noticed that in my JTextArea, there are line separators between the lines.

How to remove line separators from JTextArea in SeaGlass L&F?
Looks like it is controlled by a system property SeaGlass.JTextArea.drawLineSeparator. Try setting it to false:
System.setProperty("SeaGlass.JTextArea.drawLineSeparator", "false");
I found it in TextComponentPainter source.