Robert you can try a test user:

sharon

sharonkat

Ok, it's work for gusts too. Please use this CSS code to fix the issue:

.wpforo-widget-wrap .wpforo-widget-content .wpforo-list-item-left img {max-width: 100% !important;width: 3vw;}

You can put it in Forums > Settings > Styles > Custom CSS Code textarea. Then delete cache and do CTRL+F5 twice.

I'm not a programmer and hesitate to do it,

I can ask someone to do it or can you add it to the "to do list" for next release?

It is not urgent and my site will go live around 15th. of January. 

And if I'll add the code, will it stay there after the next update?

It works, Thanks