Good idea but it needs some work. I get the reason of having hashtags is to only reveal the attempt to connect when the intent matches, but with arbitrary synt

Good idea but it needs some work. I get the reason of having hashtags is to only reveal the attempt to connect when the intent matches, but with arbitrary syntax allowed you will get a lot of false negatives when your chances of people even matching their timeframes are low as it is. Instead offer a few predefined categories of tags, and the user can select one or more of them. That also improves the UI as you can now offer autocomplete in that field and lower the barrier of entry (removing option paralysis).