The price of the BLONs this November is pretty good, it's a steal at USD26. Too bad the fit is atrocious and blocks almost no noise when you're in the train. Since the fit isn't as snug as other IEMs, the bass quantity is lowered to a level that I appreciate while keeping the mids and highs fairly well.
even with snug seal, the Blon seems to have smaller isolation than other IEMs that i own. i agree with you that the Blon is one of those IEMs that doesn't suffer too much on the mids and treble when it shifted a bit on the ears.
In general the multi BAs without vents tend to have better isolation than DDs like the BLON. DDs with their bigger profile (in general) and vents usually have poorer isolation, but even so, the BLON is one of the weaker isolating DD IEMs IMHO.
I personally won't recommend the BLON as a transit IEM due to this. Cause one would tend to boost the volume higher to overcome the surrounding noise and that's not too safe for hearing longterm. Maybe foam tips might help with isolation a tad. YMMV.