A couple of days ago, a player from Manila started chatting to me in filipino (he addressed me by my screenname), obviously because I live in the Philippines. I don't speak the language, don't have a clue what he said, and was going to reply to that effect but I was multitabling so it took me a minute to respond.
Another player on the table (english speaker, didn't check where he was from) suggested we might be colluding. I replied quickly that I didn't speak the language and that I didn't understand what the Manila player had said, but was surprised by how quickly the collusion suggestion was made. I usually just type "english pls" whenever non-english chat occurs.
I'm sure collusion occurs online, and probably more frequently than I think. However, I'd warn against jumping to conclusions without evidence like obvious softplay (anything more sophisticated than that isn't going to occur at microstakes).
fwiw, they'd have to be absolute idiots to collude and chat to each other at the table, so don't think the presence/absence of chat at the table means anything.
P.S. agree that the flowers are similar but not identical. When I see that, I sometimes check where they're from, but more out of curiosity than anything else.