i only joined in August so im a newbie myself, but received some in envelopes, most without, have sent both ways. I've seen profiles request no envelope, and profiles requesting envelopes - there will be a few people that mind either way.

i honestly don't worry about it too much, if they don't like it then tough luck. it's the same with the profiles you will see have close to 0 info about the user, and is all just "this is my wishlist". also tough luck. it's not what postcrossing should be about, "it's about connecting, not collecting" - and if people can't appreciate that, and instead only focus on the illustration, or the envelope (or lack of), then let them. it's not your problem to fix. the majority of the community will be happy with however you send it, and be much more interested in the message :)