Which is correct and as it should be.
When using the {articles} tag, you will most likely have multiple articles being output.
And you do not want to have:
Article OneArticle TwoArticle Three
So the <br> is added by default, so you get:
Article One
Article Two
Article Three
You can of course remove that and alter the code any way you want. The editor button is just to get you started with the syntax.
Hm, I dont think, that the <br> "as it should be" there. We have a field "Separator" in the dialoge to add a spearoter if we want to have some separator.