Oh confirmed @saquetim this is a side effect to be aware of.
The issue does not happen in Firefox… but it kind of chokes.
Overall my tip here would be to avoid CTRL+A on a topic cause you will get the sidebar and a bunch of mess.
Instead CTRL+P, which will bring up the print view: https://meta.discourse.org/t/cannot-ctrl-a-to-select-and-entire-topic/336047/print
This view is far better fit for purpose given it has a print stylesheet and CTRL+A works great there.
Not sure if we can restore the old behavior on Chrome cause by restoring it we may end up breaking triple click on a post 