I think one of my worst crimes was probably not using capitals for names, and a maddening amount of shyness in my character's personality. (Though, didn't we all do that last bit?)
Yesssss, I was one of those people who knew where a period went, and I had a serious phobia of power-playing another person's character (therefore never doing it.)
SIGN UP SHEETS
Don't even get me started. Those were just the absolute WORST back then. Put in three words for each category and call it good, right? I remember the very first time I used some descriptors in a sheet; I was ecstatic. One step closer to the skill-levels of my peers.
Looking back on those, I hardly even recognize some of my OCs. I love showing the stark comparison between the "then" sheets and the "now" sheets. It's truly been a journey.
AGE
This was another thing that only fixed over time. I started RPing when I was... t w e l v e . . . ? Many of the RPs at the time were with people playing 16-to-18-year-old characters and I was down there, uncomfortable with going past 13. I cringe, remembering all the times I tried to join in spite of the "age limit" set for the RP and asking for an exclusion from the rule. I kinda still do this, since I'm not comfortable playing a character above 19 or so, but that's a story for a later time, I suppose.