Do feminised seeds grow into hermaphrodites?
Basically, NO. However this is one thing that needs clarification because there seems to be a lot of misconjecture about it.
Whether you're using regular pollen or feminised pollen it doesn't matter, the same rule applies - always try to target females that are 'hermie-resistant', because you don't want that trait passed down to the offspring. In other words, hermie issues aren't a result of feminised pollen, but a result of a mother that has hermaphroditic tendencies, either naturally, as a result of stress, or both.
Some plants are more susceptible to stress than others, and thus more prone to "go hermie" (for example by heat stress or light leaks, and some strains are simply more prone than others to grow a few hermaphrodites even when conditions are ideal). If a female does throw off a few pollen bananas then yes you can use that pollen to create feminised seeds, either by self-pollenating the mother itself or by pollenating other females (the latter being the more recommended route). However, if you use a mother that has hermaphroditic tendencies then that trait can be passed onto the offspring.
This is why when breeding for feminised seeds we look for a 'strong female', one that doesn't throw off pollen bananas very easily, so as to ensure the resulting offspring are also strong. We then FORCE the stress-resistant female to induce the creation of pollen by using colloidal silver, allowing us to get pollen even from a female that we otherwise wouldn't have been able to achieve using conventional methods such as rhodelization or light poisoning.
This is why I don't recommend using light poisoning or heat stress or similar stress methods to produce bananas, because that low stress tolerance will be passed down to the resulting seeds, resulting in plants that could hermie in a less than an ideal environment. By using CS we have the luxury of choosing a plant that's stress resistant, and still be able to force it to produce pollen thanks to the CS (as opposed to stress). It's no different for when you're creating regular seeds - you want strong mothers that can handle a bit of stress.
Actually the only hermaphrodite I've ever grown was from a regular seed - I've had 100% success with every feminised seed I've grown, and approx 1 in 2 seeds I grow are feminised (giving me a roughly 75:25 female:male ratio, as opposed to 50:50 with regular seeds).