Not sure if anyone else has seen this issue. We recently upgraded our self-hosted Open Project to 17.9.0 and now we see issues with entries in the Activity windows for Open Project work packages. 
1. Pasting in an MS Excel table, the table no longer retains any of the borders. 
2. There appears to be some "hidden" extra row underneath the table. 
3. Any paragraphs below the table become right aligned when the activity entry is saved. Here is an example: 

In both Chrome and FireFox, we are receiving console messages like this: 

gravatar.com/avatar/0869a5f59e9f7a35620f56cec82cfdca?default=404&secure=false:1  Failed to load resource: the server responded with a status of 404 ()
gravatar.com/avatar/20aaef6bb5de5d90631af3e1d29ff157?default=404&secure=false:1  Failed to load resource: the server responded with a status of 404 ()
index.js:927 toolbarview-item-unavailable Object 
Read more: https://ckeditor.com/docs/ckeditor5/latest/support/error-codes.html#error-toolbarview-item-unavailable
fe @ index.js:927

I did open something in Support but probably in the incorrect project (I just noticed this is in the Stream Communicator section):

https://community.openproject.org/projects/COMMS/work_packages/COMMS-1062/activity

I created a duplicate of the accidental Stream Communicator bug listed above: 
https://community.openproject.org/projects/OP/work_packages/OP-20476/activity

Hello John,

I’ve closed one of the two bug reports to avoid duplicates. The comments in OpenProject use technology that doesn’t replicate the Excel table exactly. However, you can edit the table by copying it from Excel into the comment field and then clicking inside the table before saving. Using the two icons with stars, you can, for example, adjust the border settings and ensure that no text appears next to it (text alignment).

If you also click on the ↩ icon at the bottom of the table, you’ll insert another paragraph after it.

Kind regards,

Alexander