Here's an interesting snippet from the article regarding matrix's efforts to be interoperable with existing protocols:
We could run the bridge somewhere relatively safe - e.g. the user’s client. There’s a bunch of work going on already in Matrix to run clientside bridges, so that your laptop or phone effectively maintains a connection over to iMessage or WhatsApp or whatever as if it were logged in… but then relays the messages into Matrix once re-encrypted. By decentralising the bridges and spreading them around the internet, you avoid them becoming a single honeypot that bad actors might look to attack: instead it becomes more a question of endpoint compromise (which is already a risk today).