I think it is a good idea to enable HTTP pipelining by default in TBB. It can reduce website fingerprints on the connection to the guard node by obfuscating request vs response traffic, and if it is supported, it can vastly reduce latency. If it is not supported, Firefox should back-negotiate to
What could possibly go wrong? Worst case, we'll disable it next week when the next vulnerability is found...
network.http.pipelining true network.http.pipelining.maxrequests 8 network.http.pipelining.ssl true network.http.proxy.pipelining true