While it is not impossible that a BR type entity is playing, it's unlikely IMO. Keep in mind that anyone with the right broker can put in BOT driven orders. They don't need to follow any more of a complicated algorithm than buying small quantities at VWAP or similar.
Re Fees, I use different platforms for different purposes. One platform charges $10 regardless of the size of the position. Handy when I'm building a very large (for me) holding in a company and want to purchase single trades of large value. Another platform charges me a fixed % of transaction value. Handy when I want to buy or sell more slowly and in smaller quantities. Both help keep my costs down.
The biggest signifier ithat the big boys are playing is when the transaction value gets to be worth less than approx $500 (or whatever the value is that ASX says is a minimum transaction size). When you see them you know it's likely a fund of some type but could still be any fund taking or leaving a position. (and don't start me on why the ASX thinks it's OK that the rules are different for us retail mob).
...and at the end of the day, we all buy and sell for a variety of reasons. Sometimes we get it right and sometimes not. I'm very happy to be picking up MYL at anything like these prices when valuations from analysist's average around 40c based on 20% approx of the resource and when we all know there is a lot more resource to come. If the company was able to report on their own valuation I have no doubt it would be significantly higher. Another of those situations where the powers that be (ASX/ASIC) get to protect us all by keeping us ignorant, go figure).
Bring on that PFS and the recent drill assays
