Eyewitness - S1-E12
Continuity mistake: When the police are taking Tessa to the safehouse and they spot Richie following on his motorcycle, the cop on the back tells Tessa to get down and pulls her down in the back seat. We then cut to a long shot of Richie following the car, and Tessa is sitting up on the passenger side. When the police pull over to arrest Richie, the cop in the back seat is again holding Tessa down. (00:34:30)
Richie Ryan: Come on, do it. Come on, come on, go ahead, do it. When the Quickening knocks you on your skinny little ass, MacLeod's gonna be right there to help you up. I die, you go right behind me.
Question: In all the Highlander movies and in this show, was there any reason given why immortals can't fight each other on holy ground?
Answer: Not directly. But there is a penalty involved. In Highlander 3 the fighting on holy ground resulted in the destruction of one of the weapons. In End Game several immortals are murdered whilst on holy ground but no repercussions were ever revealed, so it's possible it is specifically about the fighting. Nobody knows what happens when an immortal is killed in a duel on holy ground but it's safe to assume the penalty will be severe because all immortals respect this rule, even the most evil ones (except that one moment in Highlander 3).
Answer: In the episode "Little Tin God," Joe Dawson mentions a duel between immortals on a temple in Pompeii—just before Vesuvius erupted. Whether the two are supposed To Be connected is up for debate, but still.