Signing the petition is not going against democracy
Firstly, a petition of this size = the issue gets discussed in parliament. This is no undemocratic, it is quite democratic that the fact that a lot of people are unhappy about what is happening is discussed by decision makers even if it doesn't mean they hold another referendum - because they need to take heed of the mood when deciding how to progress with a brexit that so many people don't want
Secondly, as I said before, a second referendum is not undemocratic. It's a referendum and its not unprecidented to have multiple referendums on the same topic whenever public opinion shifts.
Even if that happens…. referendums aren't in our constitution anyway, so it's still not undemocratic, it's still up to our democratically elected parliament whether we do go through with brexit or not this is true whether we have a second referendum or not
The referendum is supposed to give the decision makers a true picture of public opinion