Have a look at that person's profile - if it's a guy (for example) and he's following a large number of female profiles, but very few people are following him in return, then that person's intentions are pretty obvious. :)  It's what we call a red flag.

Shirleen: First let me make a suggestion about the way you wrote you topic sentence. "How to tell someone here is not only for language study but also dating?" ... "not only for language study, but also dating" means that italki is for language study AND for dating. I know that is not what you meant. The problem is where you put 'not'. So, the correct way to write it is "How to tell someone THAT ITLAKI is not only for language study but also dating AND NOT FOR DATING. Second, tel the person "I am only interested in learning English/French/Spanish (the language you want to practice). You can also say "I am not interested in dating". If they are not interested in language, then just stop talking to them and block them. Everyone who has made some comment, has given you good advice. Don't worry about hurting anyone's feelings.

I'm not quite sure I got your point. Do you mean you how to tell someone this is the place for language study not dating?

I completely understand you! I wrote an entry in my notebook called How to find a partner on italki? I think it could be usefull to you. This is the link: http://www.italki.com/entry/562164

Easy! If someone send you an message asking for naked pictures, which city do you live in so they can come to see you, or see your face without introduction or gets horny or explicitily say they are looking for girlfriends then YOU MUST BLOCK THEM. I BLOCKED A LOT OF GUYS FROM HERE.