Hi David,
Something I sometimes notice is unfamiliar, new or visiting pilots not being greeted by any local pilots. The new or visiting pilot is left to his her her own devices which may include being confused about local protocols. It seldom hurts to smile, wave and say hello to pilots we don’t recognize. Sometimes this gets them talking about concerns they may have that would be helpful for everyone’s sake if these are addressed. This goes a long way toward creating and maintaining goodwill among the freeflight community and could avert a CraigslistCertifiedPilot™ from becoming another statistic among other things.
It’s important to remember that anyone who otherwise follows FAR103 and 36 CFR Ch II is free to engage in unpowered ultralight vehicle activity anywhere it’s not otherwise prohibited even if it means getting injured or killed in the process.  This is anyone’s prerogative and who are we to stand in their way*? We may however be able to help influence them along a better path beginning by merely extending a welcoming greeting.  The key word here is, ‘influence’. It’s typically the best we can do unless we control the property and have the authority of law–and we have neither. Please do not forget this.

* There are few exceptions including among other things the LPS Act (if we believe the prospective pilot presents a threat to themselves or to others we can call 911 who can then put them on a 72-hr hold). There have been suicides by hang glider and possibly by paraglider. If we notice a pilot is highly agitated and likely to harm themselves or another then a call to 911 is probably warranted before the fact.

Cheers, Jonathan