For example, a "stack" or a "filter" or a "queue" all have specific meanings outside of programming, their nature hints at how they work, even if the technical meaning is obviously different.
Not knowing what any of the things were leaves you with a hazy concept of what they are until you understand their English analog.
I still think it makes sense to try and explain concepts in the language in which one is most proficient, then worry about English later.
That's how I played all games as a kid :) Civilisation + dictionary FTW
It's more difficult to try to learn one ignoring the other IMO. I had collegues that didn't care much for english, but it was surprising how good they were at parsing other people's code and understand how libraries and APIs worked with very few hints.
Since being able to ask difficult, technical questions in your native language would make it easier to learn, I don't see what's so bad about that. Yes, it fragments the community, but it also recognizes that the world is not English only. Right now there's large Chinese, Russian, Japanese, and French communities that are second-class citizens without a tool like Stack Overflow.