So the journey I take to work (southeastern) the ticket barriers are always open in the morning. I usually still put my ticket through the machine regardless as I am scared that if I just walk through (regardless of having a ticket) my ticket will not work at the barriers when I get to the other end. My boyfriend tells me that this is nonsense and that I can just walk through with out putting my ticket into the machine if the gates are open but I wasn’t sure and too scared to try!
Yes, you will be able to get through the barrier at your destination.
It’s common for barriers to be open at certain times of day, in which case you don’t need to put your ticket through. Some stations don’t even have barriers at all!
Since you mention Southeastern, it’s worth being clear that this applies if you’re using a National Rail ticket, either on paper or a digital format, but rules are different if you’re using Oyster or Contactless Pay As You Go in/around London. In that case, you must always touch in and out so the system can determine how much to charge you; if you touch out without touching in you’ll be charged a maximum fare, usually £8.60.