The icons that appear next to each account in the 'Accounts' tab are not currently working properly. They only appear for some accounts, but not all, so they displace some of the account names (but not all by the same amount), and just make things harder to see.

Is there a way to hide them?

I doubt it. Which version of KMyMoney under which operating system do you experience this?

KMyMoney
Version 5.1.1-2cc89fc on Ubuntu 18.04 64bit.

It happened with prior 5.1.1 builds as well (I don't remember when icons were introduced).

This is a pretty recent version. I wonder, for which account type you see this happening. I am unable to duplicate this behavior here. It's a mystery to me how this can happen. Is this with an AppImage version or do you build yourself? Maybe, we use icons that are not installed on your system. Can you check against an AppImage version and report back?