About

"First!"is a cliché comment written by internet users to mark their initial discovery of a previously uncommented post. Due to its insubstantial nature, the practice is often perceived as a type of trolling behavior meant to frustrate and annoy other users. While the phenomenon remains most prominent on the English-speaking web, similar methods of chain commenting have been also observed on non-English language websites.
Origin

According to the Wikipedia[5] entry for “First Post”, the first English-language website where the commenting practice became a noticeable issue was the technology news site Slashdot,[1] which launched in September 1997. On the site, the first comment would be displayed above the rest in chronological order, often resulting in users replying with “First post!” or “FP!”