My native tongue is also German, and I can confirm your statements.
Well, it's just anecdotal evidence, but here are my observations:
When I'm writing text in English, I take more time to express my thoughts, rewriting passages until I think they actually express what I mean. This might make my statements more precise and thought-through than otherwise. I have especially noticed that effect on IRC: While, when I'm in a German channel, I just write my thoughts down as they come, in #lesswrong, when I'm trying to make a point, writing stuff takes longer, and the discussion might have already flown on once I'm ready for submitting my ponderings.
When I'm writing text in English, I take more time to express my thoughts...
I think that I might be an outlier in that respect.
I was really bad in school (or didn't care / couldn't deal with the setting (probably complex reasons)) which resulted in a noticeable deficit when it comes to punctuation and spelling in German. Which would result in a lot of criticism and ridicule and therefore caused me to largely avoid textual discussions in German.
So how come I ended up taking part in English discussions instead?
A relevant fact here is that the first online...
Interesting new paper (anyone have a link to an ungated version). Abstract (emphasis added):