Ping is sonar jargon.... You can let someone know about an article they might like to read by 'pinging them' to an article.... type their name in and they will see it in their comments. Some people have "ping lists" of people who like to follow particular issues.
"bump" and BTTT (Back to the top) just means someone liked or agreed with the article but had nothing to say about it... So they "bumped it to the top" of the latests comments page by making a reply so that other people would see it.