Adding a hover pop up after selecting a word/phrase could be a nice feature. It would be easier to implement if I had my own database of definitions/translations instead of relying on external dictionaries in an iframe like the current sidebar. Note that one of the reasons I've avoided implementing important features on hover so far is to ensure that everything works well on touch devices.

Not sure how to enable selecting text in a nice way given the current UI. Would probably need a way to temporarily disable the current word selection feature. Hmmm... actually one way would be to add a keyboard modifier to temporarily enable native OS selecting for advanced users without cluttering the UI for regular users.

Personal word lists: I've avoided tagging, folders or lists for organising words so far because I don't think I'd personally use them, but it's certainly something I'll consider for the future, especially if enough people request it.

I'll keep your suggestions in mind, and if you want to encourage the development of any specific feature please add or vote for it on the uservoice page: https://readlang.uservoice.com/forums/192149-general/filters...

Thanks again!