"呵呵" (hē hē), a mimetic word of happy laugh or smile originally, has been voted as the word that hurts people the most in online chatting.
"The laugh implies an underlying meaning that you will never understand". Cyber users have summarized its only function: "to irritate the other people most effectively and throw cold water on their enthusiasm".
In fact, "interesting" in English has the same function.
According to the Cambridge International Dictionary of English, "interesting" means "holding one's attention". Thus, when a native English-speaker says "It's interesting" or "That's an interesting idea", we always tend to think it is a consent or compliment.
英语单词interesting，根据权威的剑桥英语词典，意思是：引人注意 (holding one's attention)。汉语通常译为“有趣的”，所以听到美国人说“It's interesting” (很有趣) 或“That's an interesting idea” (有趣的想法)，中国人一般都理解为赞同或夸奖。
However, it's not always the case. The context is everything.
If "It's interesting" or "That's an interesting idea" is followed by the speaker's eagerness for more details, or the speaker's willingness to continue the topic, it is really a consent and compliment. But if the speaker turns to another topic, it implies his/her disagreement, and is equivalent to "那可是个奇葩想法" (It sounds weird) in Chinese. "奇葩" (qí pā) here means "weird" or "unbelievable".
如果在说了“It's interesting”或者“That's an interesting idea”之后，显出“愿听详情”的样子，或者顺着话题分享同感，那表示闻者确实是真有兴趣，很是赞同。但如果下文是转换话题，迂回敲击，那便表明，闻者并不赞同。 “That's an interesting idea”相当于汉语的“那可是个奇葩想法”。大家都知道，这里，奇葩的含义是怪异、离奇、不可思议。
In most cases, an English-speaker will reply to you politely with "It's interesting", if he or she shows no interest in what you said but don't want to let you down abruptly.
In online chatting, when a Chinese netizen disagrees with the others' words or don't know what to say about something, he or she will use "呵呵" as a perfunctory reply, which is the same with "interesting" by the native English-speakers.
Some netizens even said, "(We) hate those who always say '呵呵' the most. If they are strangers or colleagues, it doesn't matter. But if they are your classmates or e-pals, stay away from him or her as soon as possible, cuz they regard you as nothing more than a stranger."