On the original topic, people have varying definitions of cheap and frugal. As always, I've seen very few things in the ERE forum characterized as cheap. Whereas on other self-identifying frugal communities, a lot of things I don't find offensive at all are characterized as "cheap."
To me, "cheap" means being either dishonest in order to save money, or really discomforting people just to save a dollar or two. So for instance, taking a whole ton of ketchup packets when buying fast food, or taking a roll of paper towels from a public restroom, qualify as cheap. They're dishonest. On the other hand, re-using old soda bottles as water bottles, or picking up some furniture from Craigslist rather than the store, is "frugal". But on other communities, it seems that people use Jacob's favorite, the Wheaton scale, where people two levels more frugal are automatically "cheap." For instance, many people seem to consider virtually all the tips in the Tightwad Gazette as "cheap".
On the topic of dinners, Most of the time I assume people are going dutch; this seems more common for people in my social circle than splitting evenly. Of course, this has its own problems. If there are 4 or more people, someone will *always* underpay, not figuring in their tax+tip, and someone else will have to cover for them. (This qualifies as cheap, if you're taking notes).
If I feel there might be some ambiguity, I will usually request a separate check. But some restaurants don't accommodate this. Also work-related dinners are usually, but not always, sponsored. If someone is visiting from another city, they'll usually be able to put a team dinner on their corporate credit card. So it's trickier to know in advance what to do there.