Why does it even matter? When we type on the internet or anything unimportant people should be allowed to write however they wish. I get so bored of always typing "good" for school that I like to shout out with my messages when my typing is not related to school. GO CAPS!
It really comes down to a balance of how you want people to react to you.
That the internet is 'something unimportant' is somewhat misleading, since a huge proportion of all communication in the world takes place on the internet today. On a forum, you may not wish to conform to standard grammatical practice, which I'm not saying is good or bad (it's within your rights), but you will observe the following trends:
1) People will not take you seriously.
2) People will get annoyed at you.
3) People will not be able to understand what you're typing easily.
As I've said about a dozen times now, grammar is only important insofar as you value the ability to communicate. This is why I personally use as perfect a grammar I can at any given time, unless I'm in a context where I'm sure everybody will understand my abbreviations/slang.
Talking in CAPS generally does the following:
1) All of the above for poor grammar, plus:
2) People find it harder to read because all the characters are the same height.
3) People will get a headache reading text.
4) People will react hostilely to your 'shouting'.
(Ranting on for a bit...) my recommendation is, in a forum, never to post more than three words in all caps in a single post, if you ABSOLUTELY HAVE TO. And, like Ninjacube points out, there's a good way to type to
emphasise something and not look like you're shouting...from this, caps can be acceptable if there's no such thing as bold where you're at, although using the MS-Word markup for bold, surrounding a phrase with *asterisks* is also good. Also,
italics emphasise, but also quote and is generally not as strong as bold.
Also, it is unadvisable to underline text on a forum or electronically unless it's automatically done in the form of a hyperlink, because this also makes text difficult to read. I'm not sure you can underline stuff manually on this forum.
Personally, if I'm feeling silly and my tone is sufficiently lighthearted enough for people to conclude that I'm not shouting to scare them but just to be an idiot, then yes, I'll use caps then: "OMG, YOU CAN'T BE SRS!?!?" ...but please, use your discretion wisely.
