Recently there is a user gave an ID of my observation. When I clicked his/her profile, the user stated that he/she is a collector in the biography. Can I block this user in iNat? Thank you.
If you’re absolutely sure it’s the right thing to do, open your profile settings, there choose contacts, scroll down and there’ll be an option, but remember it’s 3 people max.
or ask help at iNaturalist.
I’m confused about why you want to block them?
the concern is that by “collecting”, they’re poaching specimens of rare/endangered organisms. there might, ofc, be some misunderstanding.
Does blocking a person stop them from seeing the blocker’s observations or just from commenting on or identifying them?
It stops the blocked user from seeing the blocker’s observations, as well as messaging or following them.
I assume it also utilises the mute function which just removes any notifications from the blocked user.
Thank you for answering. I speak the same language with that user, I don’t think there is any room for misunderstanding 
I found that blocking people cannot stop them from viewing my observations, so I changed all my locations of less mobile organisms into obscured for now
Blocking people cannot stop them from viewing observations if they’re not logged in (and perhaps also using a different IP address). The web interface allows unregistered visitors to explore observations and filter by user-name.
Why do you want to block a collector (of insects, presumably)? Just because they are a collector? This seems a bit petty, honestly, as you are blocking a person solely based on the fact that they collect. This person could be useful to you in the future.
In addition, why would you stop someone from even knowing your ID, the specific location, or whatnot of your obs? Just because they collect?