You are developing a software based on various modules. Each module is considered an Epic in JIRA. When the module is accepted by the client, the PM closes the Epic. After some time the client demands a new feature in the module. Do you a) reopen the Epic (which is not a out of the box step in JIRA) or b) create a new epic with the same name (or a similar one) or c) don't treat it as an epic at all (given that this is a small feature request that it may be treated in one sprint) or d) any other idea?
You create a new Epic with a similar name
The key point here is this:
after some time - if the customer already signed off on the original feature, it was right to close the Epic. If they've essentially now got new requirements and wish to enhance the feature, by all means track it in a new Epic named something like 'Feature v2'. I recommend you find out their other requirements as it may be that the enhancement to the existing feature is just one of many forming a Feature Set.