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Hi Malte, Even though technically and logically it should not hurt your sites, I do have some experience in this where I had seen rankings and saturation affected when I had added unrelated websites into my GA account for easier management. Of course this could have been coincidental or perhaps I was being paranoid. But I could not find any other explanation (as far as my investigation went) for this.

go for it, I agree with Stores, it will help rather then hinder. I set up a test to see just how well bold helped keywords, the test were inconculsive, I suggest it has only mild benefit. i believe SEOMoz has shown the same. What you suggest is quite natural, iwould tr5y to get the guts of the subject into that paragraph