It seems to be just this question that's doing it for me, and the posted non-answer indicates it's not just me.
This is " Zalgo text". Basically a way of misusing unicode characters.
Z̢̮̞̠̠̾̇ͬͩ̆ͩͧ͑̌̅̾̽̿̀̚a̴̻͈̟͍̳̣͓͍͇̻͎͔̟͇ͫ̀ͨ̽͋̈́͗͘l̢̛͓͙̹̯̦̞̞͔͎͊́̈́ͣͨ͌͗̐̓̓̔̔͋ͪ́g̯̤̩͓͇̹̖̪̝̃͌ͩͨ̃͗ͫ́̂̉͐͂̇̃̀͟͡͠ͅo̢̹͓̻̖̤̫̝̟̰̯͖̻̱̤͎͙̱͊͐̽ͦ͊ͨ͒̽̇͊̍̑̚̕͘̕ ̶̨̻̦͔̟̟̰̹̫̭̰͙̭̺͙̐͐̓̓͆͗ͮ͛ͯ̉ͫ̾͂ͯ͑͐́́͞t͒͛ͧ̈̑ͣͣ̇͊̍ͯ̑̀̋̆͌̚̕͢͟͝҉̺̝͕̰̣̗̭̳̥̜̯̝͔͍̞̦͔̹ė̢̐ͮ͗͏̡̠̬̘̲͕̬̝͍̤̟̹͖̥̲͇͎̗̱̺͠x̢̛̼̦̺̘̦̮͔͑͆̾̈͗ͫͥͫ͛ͤͤͮ͒ͅt̑̽͑̑ͨ̈́̐̌̏ͬ̆ͮ͑ͭ͛ͭͫ̓̚҉̢̨̗͇̱͖́͢ ͔̭̰̻̰̼̔ͩͩͧͣͮ̿̆̕̕ỉ̡̩͉͉̪̘̼̘̗̱̬̺̂̐̄ͦͬ̋̉͑̅ͯ̿̿̂͑̓͘͟ͅs̛ͭ͆ͤ̓͂͌̇ͪͭ͌͛̉̄ͨ̾́͊̀͝͏͚̰͇̯̖̙̼̲͎̣̦͍͙͎͕͡ ̵̷̡̙̻̪͙͙̫̪̱͚̯͕̺͛̌̐̇ͣ̾̔̓̔ͯͤͫ͜͡f̸͖̫̯͖̮̺̼̗͉̞̫͕̤̼͈̅͊̄̐̂̅͐̉ͧ̔ͫͦ̅͡ͅͅư̌̽͐̏̑̑̄͠҉͍̥̰̟͍̫͚̺̜̩̜n̡̧̼̪̱̯̺̥̳̝̻͍̭ͬ́̀̍͐̾ͧ̓̋͒͋͊̇̾͂̋̚̚͟͡
You can generate your own here
A pair of accounts were created to post this mess. As @Richard states, it's "Zalgo text" (Stack Overflow has an explanation here). I've deleted both accounts.
From this SE meta post, the ability to do this is by design:
By Mark Gravel comment this is to be considered as now by-design and as such won't be modified unless problems emerge that make the fix worth the effort. In the meantime abuses of the system shall be dealt manually.
Since I feel that the contents of an element (in this case the
div containing the answer) should not be allowed to draw outside the boundaries of that element, I've filed a bug report over on central Meta.