Good read on the subject here - https://www.wired.com/story/signal-mobilecoin-payments-messaging-cryptocurrency

Forum thread if you want to gauge users opinions. There’s some good discussion/conjecture, some are mixed on whether this will alienate existing users or be something that actually makes sense later on (with points made that the fees for this coin could be used to fund Signal development and the like for example) - https://community.signalusers.org/t/signal-blog-help-us-test-payments-in-signal/30817/71

One users take on using this feature here -

I just tested the process of adding funds and sending money, and it works fine. It took less than a minute to transfer just short of half a MobileCoin from an exchange to my Signal wallet.

Then it took a second or two to transfer 0.24 MobileCoin to another Signal user.

However, at a cost of 0.01 MobileCoin (nearly £0.50), I dare say this is a non-starter in the UK (except maybe for people superbly concerned with private payment privacy) where we are used to free instant bank transfers, Paym (same but using mobile numbers instead of account numbers), free Revolut transfers, etc.

To top that, the process of obtaining MOB in the first place was quite convoluted - I had to obtain BUSD first, then send it to FTX to be converted into MOB. Who would go to such lengths for casual small payments? Not anyone I know. My use cases would be when a bunch of us go to a restaurant and share the bill, when we gather up to buy someone a birthday present, or when we buy e.g. a streaming subscription together and need to settle up. We have so many free and much faster ways to do that, both in the UK and Europe, from bank transfers using real money from our banking apps, to Revolut, N26, Monzo, Starling, Wise, even Curve will do transfers soon… The list is ever growing.

It is an interesting feature but at the current level of complication and cost I don’t see it gaining any meaningful foothold in the UK or EU.