I'm sure shifting without the clutch does wear your synchro's, however, if you do it well, although you probably wont get it quite bang on, it will be close enough such that it minimizes the wear on your synchro's.
i shift without the clutch every once in a while when i'm too lazy to move my left foot.
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Hot: 2001 Estoril M RoadsterZCP 19's michelin supersports, ZHP knob, JL 8W3
Cold: 2002 TiAg M3 6mt
deoranged, dechromed, led tails, ZHP knob, UUC SS v3, GROM, OEM 18's w310's,
Fun: 2006 YZF-R6, black, ohlins, pazzo, cat delete, vance hines csone, YEC racing tune