Text-underline not visible when setting or editing it

I used to absolutely LOVE ❤︎ Workflowy.

Until I started to experience after a while that I needed more sophisticated productivity functionality (ability to add images, ability to add due dates and reminders, ability to add colour for markup, etc). 
The strength of Workflowy was and is its power in simplicity (love it!), but it at the same time became also too bare-bones for me to be really useful in my workflow. And there did not seem to be any or much progress being made in the further development of Workflowy, unfortunately. So I briefly checked out Dynalist (for a few days... I still liked Workflowy better) and then went back to Evernote, since they finally woke up and improved their free webversion considerably compared to (the horrific web version) a few years ago.

I recently -just for good old times sake- had a look again at Workflowy and discovered that finally new functionality is being added. Good to see! 'All good things come to those who wait' as they say apparently in England ;-)

So I decided to sign up for the community to see what's cooking here. 

/end of introduction

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A noticed a tiny small UI/IX thing, but I don't know if this is simply Windows related or something else. I am using Windows 7 (yes!!!) on the PC of my parents at the moment and what I notice is this, when it comes to making a text underlined:

- You select a text that you want to make underlined
- You click [Ctrl-U] (on Windows)

Then nothing appears to happen. No underline appears under the blue selection. It is only when you click your cursor away from the text-selection that the underline appears.

Why does the underline not appear inside the blue selection when you click [Ctrl-U]?
On [Ctrl-B] and [Ctrl-I] for Bold and Italics it works as intended, you can see the results immediately appearing without needing to click outside of the blue selection.

Image above shows the selection that is actually underlined
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Image above shows the text after clicking away from the selection
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(This is on Windows 7, using the latest Chrome browser or latest Edge browser).

Any ideas why this happens?