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Any legit way to determine how many bots?

Out of 414,587 accounts created by SteemMonsters, 3,891 has made a single comment/post on Hive.

Can't really deduce much more than that, but I think it's fairly obvious.

Can we look at the way tx are signed?

Well, we can easily deduce which accounts are active on Hive and which only play Splinterlands, but I am not sure you can tell which ones are bots on Splinterlands, and which are not, outside of maybe how long they play for. (bots likely play for a better part of the day).

Not sure it's really worth the effort as I am pretty confident a large percentage of them are bots.

Yea, all cool ...