@Override
	public boolean applyTo(Program program) {
		CodeUnit cu = getCodeUnit(program);
		if (cu == null) {
			message = "No Instruction or Data found for address " + address.toString() +
				"  Is this address valid?";
			return false;
		}
		String previousComment = cu.getComment(commentType);
		String newComment =
			(previousComment != null) ? previousComment + separator + comment : comment;
		cu.setComment(commentType, newComment);
		return true;
	}
Construct command
@param addr address of code unit where comment will be placed
@param commentType comment type
@param comment comment for code unit, should not be null
@param separator characters to separate the new comment from the previous comment when
concatenating.
Ghidra/Features/Base/src/main/java/ghidra/app/cmd/comments/AppendCommentCmd.java