I used seán as a username once. I gave up after I realised it was fine on my own personal computer but once I jumped on to an azerty keyboard or something simpler tasks just became more difficult -- finding the letter with a fada just results in searching the charmap rather than keyboard.

You can have fadas in URLs e.g. seán.dev using a technique called Punycode.

Ogham is another Irish script and is vertical but unique in Unicode because its space charcter is a line - the only language to do so.