Yea, I was thinking about that.  I'm not convinced that a `5ms` lower bound makes sense... to your point, maybe it shouldn't be `250ms` either though.

There are three states:

 1. `max_in_flight = 1` behaves essentially unbuffered regardless of volume.
 2. `max_in_flight > 1` and low-volume topic. If you want to prioritize delivery latency, the appropriate configuration is to *disable* output buffering (we should document this).
 3. `max_in_flight > 1` and higher-volume topic.  You can either prefer throughput (at the potential cost of a *maximum* delivery latency that can be set as low as this value) or disable output buffering to prioritize delivery latency.

I guess my argument is that you can't really have everything (which is what I feel like this was trying to do before).  I like how it's still possible to prioritize latency with this value lower bounded at `250ms`, it just means consciously choosing that tradeoff.

Ultimately, it's not the end of the world to allow it to be configured that low, it just needs to come with some disclaimers.  But is there a better lower bound?