The ' is HTML code for a "curly" or "smart" apostrophe. This is a character outside the basic set and must be specified in HTML with a special character code, which in this case is '. The software is reading apostrophes and trying to turn them into HTML code and failing.
The trouble is, when you post an '&' to the forum, the software translates that into the HTML code for an ampersand. The causes the HTML character code to be escaped so that it displays the code rather than the curly apostrophe that was intended.
Then there are some forums and blogs that have a bug in them that leave out the semi-colon when they turn apostrophes into HTML code which doesn't work at all.
If that made any sense to you, that's what is happening and yes, it's very annoying.
Female, 5'3", 50, Max squat: 202.5lbs. Max deadlift: 225 x 3.