Back in Dec, my guess was those are the same bot selling and...

Back in Dec, my guess was those are the same bot selling and buying between themselves, no net impact and hence no disclosure requirement.

Apparently it only costs 30 cents per $15k in trades for ASX clearing fee, which means Comsec makes $29.60 for each brokerage charges they make

https://www2.asx.com.au/about/regulation/clearing-and-settlement-of-cash-equities-in-australia/clearing/clearing-services-and-pricing

ASX Clear will charge each participant a transaction clearing fee of 0.225bp of the transaction value.The clearing fee = 15,150 × 0.00225% = $0.34 per participant.

But even at this low 22.5 cents per $10k brokerage, buying and selling $30m of shares is still expensive, so either they are getting even better deal as "market maker" from ASX, or they were losing money on those AI bug.