LinkedIn character counter
3,000 characters, cut at about 210
LinkedIn folds the post after roughly three lines. The see more link is the single biggest lever on a LinkedIn post, and it sits at character 210, not at 3,000.
Line breaks survive, and they matter
Unlike some networks, LinkedIn keeps your blank lines. A wall of text and the same text with breaks perform differently enough that it is worth counting both.
Echoia does the rest: publishing to ten networks, every comment and message in one inbox. Free for three accounts.