1 - current / 2 - oldid (probably will fail) - Huh, it worked...

(3 - miscopied found...)

[2] vs. [2] vs. [2]

[10] vs. [10]

[2] - Huh I wonder why copying this from Special:Permalink/906259108 works...

[10] - ...but copying this from Special:Permalink/906082941 doesn't work.

Perhaps old revisions behave differently...

Then how about copying this from the current revision: [9]

Which works for some reason... so it must be a rendering difference in old page versions that sometimes causes clipboard data to be different.

(The edit summary for this latest edit was intentionally left blank, something I don't normally do; I try to write an edit summary on every edit.)