There is no documented way to suppress warnings about missing 4 byte UTF-8 support

I thought we had made that an INFO, assigning to stefan.r as he wrote that code.

+1

Corrected the version number.

The version number isn't changing, but it should be 7.50 not 7.5.

Could just be dev, since same problem there :)

That is not a warning, this is just information and I do not see any problem with this. I also see metatag twice, Upload progress and Translation update status as blue in status page. I also cannot get rid of these. They are just information I can ignore.

Considering these are not actually Drupal warnings, and rather informational (REQUIREMENT_INFO), Drush shouldn't be calling those "warning" either (rather "info" or similar).

It does seem quite annoying to be nagged about this all the time, I wonder if we can fix this in Drush itself? I have created an issue at https://github.com/drush-ops/drush/issues/2270

I can confirm this is really annoying. I think many many existing Drupal sites will not use utf8mb4 (instead perhaps even migrate to D8 ;)) but the messages make drush really bad to use. Really important messages are under-represented now. I'd suggest to think about removing this completely in core or add a setting / variable. I can't see a huge benefit. But that's just my opinion.
Another problem is that updating drush is a problem for users in some hosting environments where drush is managed by the hoster.

I would be okay to add a variable to turn off UTF8-MB4 info messages.

You need to fix broken drush. The issue is not in core...

Re #12: I have other REQUIREMENT_INFO active on a site but those are not drush warnings, only this.

It was Drush updb that was mistakenly showing this info message as a warning. Fixed at https://github.com/drush-ops/drush/issues/2270#issuecomment-232425690

Thank you Moshe! (I guess I picked a good example output...)

Great, thank you very much :)

I updated to Drush 8.1.2 but I still have this problem. Can anyone confirm this actually works?
Nvm, Drush not released with fix yet.

Fix now available in drush 8.1.3

So the fix is to update drush?

I think this should be made quite clear for people like me looking for an answer. Can someone please confirm?

This message is driving me nuts on my 30 Drupal installations all on the server... everytime I have to do a mass update I look twice at the screen thinking something is wrong!

Thanks in advance

#22: Yes, the fix is in the newer drush versions.

Thanks for the confirmation :)