I have used HelloTalk for over two years now. I think HelloTalk is a great idea, and overall implemented very well. I use this app to practice Japanese, and find that overall people are courteous and honestly want to learn. I quite like the Moments function, and in my experience people use it to share pictures of where they live, or ask many people for language corrections, which is great. Now, there are many superfluous posts like “ Please teach me English!!!”, but I think it is a small price to pay. I do wish that Moments allowed for video posting, though. Many times there are short clips of concerts or scenery that I would love to share with people.
As for sexual harassment, whenever it has happened, it is generally handled quickly in my experience. However, I do know of a few notorious people that keep rejoining HelloTalk despite being blocked many times. There is not much that can be done for those people, but hopefully they will learn someday. There are some people that are more interested in finding a foreign girlfriend/ boyfriend, but it is easy to find these people and kindly decline or misdirect them.
I have had this issue on an off, but sometimes my app will show unread messages, but I cannot see them. Before I would have to delete and redownload to fix it, but as of today when it did it I was able to fix it by closing and reopening HelloTalk . It isn’t a huge inconvenience, but a bit annoying at times.