I think I read it was not the Brontė sisters themselves who started putting that diaeresis symbol over the last letter of their surname. It was their father who started that affectation. I think originally his surname was something unpronounceable in Irish, before it was anglicised to Brunty. That was not classy enough for Patrick, so he changed it to Brontė. ė in a word usually means you should pronounce the letter as a separate syllable, so it's a sign that the last e is not silent. It is still breaking the rules a bit, because it usually comes after another vowel in French or French names, such as poėlle, Zoė and Noėl. What Patrick Brontė maybe did not realise, was that it would be difficult to type 'ė' on a British keyboard (and I expect on other English speaking countries' keyboards). In the past, I have either had to look up how to compose the letter, which I can never remember how to do, or had to copy and paste the letter from Word or a Windows utility. But now, I have found out how to map different letters and symbols to my keyboard, so I can type ėėėėėėėėėėėėėėėėėėėėėėėėėėėėėė as easy as that.
Similarly, I have often found it inconvenient not having easy access to the ° symbol, as it makes typing temperatures difficult. I have often wondered why there was no ° symbol, because the ~ symbol is not very useful, and then there are those odd symbols on the key in the top left hand corner, which I didn't even know what they are. Apparently one is the French grave accent, and the other is the not sign, which I think is used in Boolean logic.
However, I have only worked out how to map letters and symbols on my keyboard on Linux.