I have the same problem and can’t find any way to solve it.
Tested a lot of things under 1.2.1 and 1.2.2 and 1.3 but still the same problem. No plugins installed.
Can this issue be a server one ?
In this case what can generate that extra line ???
Please help me 2 weeks I’m looking for a solution. I love WP but if i can’t find a way to have RSS working, I will migrate through an other blog apps.
Thanks
My site is : https://krownoise.net/ and the RSS https://krownoise.net/wp-rss2.php