Hi,
to reproduce simply - select a grammar which defines folding markers etc. - type something which can be folded - place the cursor just before the greyed three points indicator - press e.g. ↩
it ends up like that:
[the problem - I can't even do an 'undo' and if I try to remove these CTRL char weird things happen]
or - place the cursor just after the three point indicator and start typing - nothing to see but the typed chars are stored within the folded block
Cheers, --Hans