I was visiting friends in Kathmandu (likely a decade ago) and had a great time exploring the mountains and the cultural areas. Also if you make lifelong friends, they might give you a khata scarf. You can also buy those gurkha knives if you can take it back home. There was also some bad people but that is common everywhere in the world exacerbated with elements of poverty so don't forget your common sense when dealing with sketchy situations. Theres also definitely pollution building up in the rivers.
Also note that the time I visited was some time after the Nepalese Civil War so soldiers still wandered the streets. However they honestly don't care about what you do, I don't know if they're still around now. As well, electricity and water would be out after 10pm so be prepared for that.