Here are some terms that are often used, and how they should be typed into the additional notes field.

Correct examples:
"...following the band's split-up, they...." (dash in 'split-up' when used as a noun)
"The band split up in April 2010". (no dash in 'split up')

"The band played thrash metal until 2009". (thrash metal and other genres shouldn't be capitalized unless they're part of a list, like this) -
Not to be confused with:
- ... (Thrash Metal from Alabama)
- ### (Black/Death Metal from Oregon)

- correct: EP (not Ep or ep), LP (not Lp or lp)
- in release notes: 12-page booklet (not 12-pages booklet)
- Digipak (not Digipack)
- CD-R (not CDR, CDr, CD-r)
- correct: '80s, '90s (not 80s, '80's, 90ies, etc.)
- correct: ...played guitar, bass, and drums (instead of) .. played guitar, bass and drums. Comma should be placed after the next-to-last thing being listed in cases like this.
- better to use 'and' than '&'.

This could be a good thread to ask questions in order to clarify, or to point out common errors on this part of a band's page so that they can be avoided.

Also:

- Comes with obi (not OBI or Obi)

While it isn't something I have paid attention to in the past, wouldn't it be more grammatically correct not to capitalize the genres in additional notes even when it is part of a list? I thought the capitals were more or less reserved just for the genre field.

https://www.metal-archives.com/bands/Sirens/13642
Here is an example. Where it says:
Not to be confused with:
-Sirens (Traditional Heavy Metal from Witten)

I don't understand why we have written Traditional Heavy Metal, rather than leaving it all lowercase.

That example brings up a couple of other issues - the genre mentioned on the other band's page should match (so 'traditional' shouldn't really be there in front of heavy metal). Similar examples that have been modified in the past included 'slamming death metal', or 'dark metal', which aren't recognized in that particular wording within the genre field.
The other issue there is that a list is being made out of one item. For the sake of saving space, I often make those into a single line instead of creating a list of one item and using two lines. Not sure what is preferred, or if it matters one way or the other.
Here's another example that can be used that has two or more names on the list:
https://www.metal-archives.com/bands/Tormentor/5331
I let Derigin know about your question, as he knows what will be the best way going forward with capitalizations in these instances.

Alright, here I brought a list of what was requested in the OP to that it can be fixed it:
https://www.metal-archives.com/search/a ... ame=#bands

Stealth, the first link that you provided is a worthwhile search for corrections, and I've been working through the same search over the last couple of days (pages 1 and 2 complete). Typing in ctrl+F and then a search for 'split-up' with the dash after clicking on that link can get you to the ones that need a correction, since the search includes ones with and without the dash.
I put spoiler brackets on the other searches that you posted in hopes of having this thread not become too convoluted, and specificially for these reasons - but thanks anyway.