It's a natural reaction in one-on-one conversations to switch to the language that least impedes communication. That's annoying when you're trying to learn a language but wouldn't be too bad as an outcome if your actual problem is just the lack of English documentation.
But in the case of a larger online community where German is used by default, you'd be unlikely to get everyone to switch to English just by posting in bad German. After all, you might just as well be a Kazakh whose English is even worse, and as just another anonymous newcomer, there's no reason to accommodate you in particular.
