Sorry to keep bluring the issue in this thread with the MIDI loop recording issue (
http://forum.cockos.com/showthread.php?t=32579), but they are possibly related.
Assuming REAPER is adjusting the time at which it records MIDI notes (based on sound card latency), it may be a plausible explanation for why the first note can't reliable be recorded in a MIDI loop even with input quantize enabled.
Perhaps REAPER is FIRST adjusting the MIDI note time BEFORE applying the input quantization. That would possibly explain why I can't reliably record the first note in the MIDI loop even with extreme input quantization settings.
Sorry for all of this speculation.