I'm also still in some IRC channels from way back, and I can't deny I hate what discord did to the IRC community. ("Look how they massacred my boy...")
Of course, Discord pulled it off for a good reason - the experience was seamless, featureful, rich, and modern - none of which IRC can claim. And it's only cantankerous sticks in the mud such as I who care about ideological concerns like interoperability and open standards.
And another thing that Discord did is to absolutely explode the channel count. In the IRC days, a particular community or friend group would make do with one single channel. But that group moves to Discord, and suddenly creates a general channel, announcements channel, music channel, games channel, cooking channel - all for one single friend group, and multiply that by the number of groups you are in - because the Discord model permitted it and made it frictionless.
And I think that's why for some people who use Discord at the moment, it wouldn't be enough to simply have a channel on a public Matrix instance. People are used to having a whole 'server' to themselves (of course discord 'servers' aren't servers, but let's set that aside) and so they'd need at least a 'space' in Matrix, being the more reasonably named analogue.

This particular cheque should work, if processed by a person.
Cheques have two fields for the amount; numbers and written out. The numerical field is the most important and required part, while the written is to deter fraud, for example the bearer may attempt to alter £100 to £1000, or £300 to £800, and having the sum also in writing makes this a lot harder.
So as long as this cheque has $650 in the number field, it should be valid.